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CHARACTERIZATION OF COMMERICAL POLYPROPYLENE BY MILD

PYROLYSIS AND SPECTROMETRY

A Thesis

Presented to

The Graduate Faculty of The University of Akron

In Partial Fulfillment

of the Requirements for the Degree

Master of Science

David E. Dabney

May, 2006

CHARACTERIZATION OF COMMERICAL POLYPROPYLENE BY MILD

PYROLYSIS AND

David E. Dabney

Thesis

Approved: Accepted:

______Advisor Dean of the College Dr. Chrys Wesdemiotis Dr. Ronald F. Levant

______Faculty Reader Dean of the Graduate School Dr. Jun Hu Dr. George R. Newkome

______Department Chair Date Dr. Michael J Taschner

ii DEDICATION

To Sally and Zachary whose support and sacrifice made this possible.

iii ACKNOWLEDGEMENTS

Special thanks to Dr. Chrys Wesdemiotis for his help and guidance through this process.

Special thanks to Dr. Jun Hu for his time and feedback.

Thank you to Dr. Mike Polce for his assistance in this project.

Thank you to Panthida Thomya for her numerous trips to Noveon, Inc.

iv TABLE OF CONTENTS

Page

LIST OF TABLES…………………………………………………………………. viii

LIST OF FIGURES…………………………………………………………………ix

LIST OF SCHEMES………………………………………………………………..xii

CHAPTER

I. INTRODUCTION…………………………………………………. 1

II. LITERATURE REVIEW………………………………………….. 4

2.1. Introduction……………………………………………………. 4

2.2. Sources…………………………………………….. 5

2.3 Direct Pyrolysis Analysis of PP……………………………….. 5

2.4 Free Degradation ………………………………………6

2.5 Types of Polypropylene……………………………………….. 8

III. MATERIAL AND METHODS…..………………………………... 10

3.1. Amorphous Polypropylene……………………………………. 10

3.2. Pyrolysis Procedure…………………………………………… 11

3.3. Initial Sample Preparation…………………………………….. 11

3.3.1. Revised Sample Preparation………………………… 13

3.4. Blank Study……………………………………………………. 13

v 3.5. Using the MALDI-TOF Mass ………………….. 14

3.5.1 MALDI-TOF MS Instrument Conditions……………. 16

3.6 Contamination Verification…………………………… 17

3.7 Data Interpretation………………………………………………17

IV. RESULTS AND DISCUSSIONS………………………………… 19

4.1. Description of Structures……………………………………… 19

4.2. Blank Study…………………………………………………… 21

4.2.1. Alternative Glass Vials……………………………… 23

4.2.2. Blank Results……………………………………….. 26

4.3. PP Individual Temperature Analysis-Introduction……………. 26

4.3.1. PP Analysis – 125ºC………………………………… 28

4.3.2. PP Analysis – 150ºC………………………………… 39

4.3.3. PP Analysis – 175ºC………………………………… 45

4.3.4. PP Analysis – 200ºC………………………………… 49

4.3.5. PP Analysis – 225ºC………………………………… 53

4.3.6. PP Analysis – 250ºC………………………………… 57

4.3.7. PP Analysis – 275ºC………………………………… 62

4.3.8. PP Analysis – 300ºC………………………………… 66

4.4. Additional PP Analysis………………………………………... 70

4.4.1. Analysis with a Higher Cut-Off Mass………………. 70

4.4.2. Oxygen Experiments……………………………...... 71

4.5. Mechanism Review……………………………………. ……... 75

4.6. Future Work…………………………………………………… 80

vi 4.7. Summary of all Temperatures………………………………… 80

V. CONCLUSION…………………………………………………….. 82

VI. BIBLIOGRAPHY…………………………………………………. 84

APPENDICES……………………………………………………………... 86

APPENDIX A. OF FRAGMENTS……………………. 87

APPENDIX B. MASS TABLES…………………………………... 90

APPENDIX C. ANOVA RESULTS………………………………. 111

vii LIST OF TABLES

Table Page

3.1. Blank study ratio……………………………………………………… 14

3.2. Monoisotopic and average used for analysis………………………….. 18

4.1. Mass designations for fragmentation structures………………………………. 20

4.2. List of common peaks: blank compared to samples prepared via different protocols...... 23

4.3. Comparison of the MALDI-TOF mass spectra of the pyrolyzates (125ºC) from replicate samples b, c and d. Only above m/z 700 cutoff mass) were recorded. An x indicates that this is observed. The masses listed are nominal monoisotopic values.………………………………………………………………. 32

4.4. Comparison of the MALDI-TOF mass spectra of the pyrolyzates from samples b, c and d (125ºC) using normalized abundances.………...... 33

4.5. Sodiated ions (nominal ) in the MALDI mass of sample d, pyrolyzed at 125ºC.…………………………...... 34

4.6. ANOVA results for common C12 peaks in the MALDI-TOF mass spectra of replicates b, c and d.…………………………………………………………….. 34

viii LIST OF FIGURES

Figure Page

2.1. Conformations of polypropylene……………………………………………… 9

3.1. Structure of standard polypropylene demonstrating methyl termination on both ends………………………………………………………………………... 10

3.2. Diagram of a reflectron MADLI-TOF mass spectrometer……………………. 15

4.1. Representative structures of PP pyrolyzates ………………………………...... 20

4.2. Figure 4.2. Comparison of blank (contained in a PP tube) to PP pyrolyzate samples prepared in PP or glass vials. Only the m/z 1000-1100 region of the corresponding MALDI-TOF mass spectra is displayed. …………..... 24

4.3. MALDI-TOF of the polysiloxane contaminant from 19 x 65 mm glass tubes……………………………………………………………. 25

4.4. MALDI-TOF mass spectrum of sample a, pyrolyzed at 125ºC. The inset shows an expanded view of the m/z 870-960 region of the spectrum.…………..... 35

4.5. MALDI-TOF mass spectrum of sample b, pyrolyzed at 125ºC. The inset shows an expanded view of the m/z 950-1100 region.…………………………...... 36

4.6. MALDI-TOF mass spectrum of sample c, pyrolyzed at 125ºC. The inset shows an expanded view of the m/z 950-1100 region.………………………...... 37

4.7. MALDI-TOF mass spectrum of sample d, pyrolyzed at 125ºC. The inset shows an expanded view of the m/z 700-790 region, which also contains sodiated pyrolysis products.………………………………………………………………..... 38

4.8. MALDI-TOF mass spectrum of sample a, pyrolyzed at 150ºC. The inset shows an expanded view of the m/z 985-1180 region.…………………………….. 41

4.9. MALDI-TOF mass spectrum of sample b, pyrolyzed at 150ºC. The inset shows an expanded view of the m/z 1000-1070 region……………………………. 42

ix 4.10. MALDI-TOF mass spectrum of sample c, pyrolyzed at 150ºC. The inset shows an expanded view of the m/z 1000-1070 region…………………………..... 43

4.11. MALDI-TOF mass spectrum of sample d, pyrolyzed at 150ºC. The inset shows an expanded view of the m/z 1000-1070 region…………………...... 44

4.12. MALDI-TOF mass spectrum of sample b, pyrolyzed at 175ºC. The inset shows an expanded view of the m/z 1000-1080 region…………………………..... 46

4.13. MALDI-TOF mass spectrum of sample c, pyrolyzed at 175ºC. The inset shows an expanded view of the m/z 1000-1080 region …………….……... ……... 47

4.14. MALDI-TOF mass spectrum of sample d, pyrolyzed at 175ºC. The inset shows an expanded view of the m/z 1000-1080 region ………………...... 48

4.15. MALDI-TOF mass spectrum of sample b, pyrolyzed at 200ºC. The inset shows an expanded view of the m/z 1000-1080 region …………………………… 51

4.16. MALDI-TOF mass spectrum of sample c, pyrolyzed at 200ºC. The inset shows an expanded view of the m/z 875-965 region ……...... 52

4.17. MALDI-TOF mass spectrum of sample a, pyrolyzed at 225ºC. The inset shows an expanded view of the m/z 1000-1080 region……………………. ……... 55

4.18. MALDI-TOF mass spectrum of sample c, pyrolyzed at 225ºC. The inset shows an expanded view of the m/z 1000-1080 region……………………………. 56

4.19. MALDI-TOF mass spectrum of sample a, pyrolyzed at 250ºC. The inset shows an expanded view of the m/z 1000-1080 region……………………. ……... 59

4.20. MALDI-TOF mass spectrum of sample b, pyrolyzed at 250ºC. The inset shows an expanded view of the m/z 1000-1080 region……………………………. 60

4.21. MALDI-TOF mass spectrum of sample c, pyrolyzed at 250ºC. The inset shows an expanded view of the m/z 1000-1080 region……………………………. 61

4.22. MALDI-TOF mass spectrum of sample a, pyrolyzed at 275ºC. The inset shows an expanded view of the m/z 1000-1080 region……………………………. 63

4.23. MALDI-TOF mass spectrum of sample b, pyrolyzed at 275ºC. The inset shows an expanded view of the m/z 1000-1080 region…………………………… 64

4.24. MALDI-TOF mass spectrum of sample c, pyrolyzed at 275ºC. The inset shows an expanded view of the m/z 870-960 region……………………………… 65

x 4.25. MALDI-TOF mass spectrum of sample a, pyrolyzed at 300ºC. The inset shows an expanded view of the m/z 1000-1080 region……………………………. 67

4.26. MALDI-TOF mass spectrum of sample b, pyrolyzed at 300ºC. The inset shows an expanded view of the m/z 1000-1080 region……………………………. 68

4.27. MALDI-TOF mass spectrum of sample d, pyrolyzed at 300ºC. The inset shows an expanded view of the m/z 1000-1080 region…………………………….69

4.28. MALDI-TOF mass spectrum of PP pyrolyzates formed at 175ºC, acquired using a high mass cut-off..…………………………...... 73

4.29. MALDI-TOF mass spectrum of PP pyrolyzates formed at 300ºC, acquired using a high mass cut-off………………………………………………… 74

xi LIST OF SCHEMES

Scheme Page

4.1. Initial cleavage of bond I followed by H* loss to form truncated PP chains with olefinic chain ends.……………………………………………………. 77

4.2. Backbiting rearrangements in secondary radical 1* followed by β-scission.…..78

4.3. Backbiting rearrangements in primary radical 2* followed by β-scission.…..... 79

xii CHAPTER I

INTRODUCTION

Poly(propylene) “PP” is a derived from vinyl monomers and

belongs to a class of economically important which are commonly known as

polyolefins. PP is currently one of the most commonly utilized polymers for commercial

applications. Since its commercial production began in the 1950’s, PP use has grown

steadily to become one of the top use commodity polymers today.1 Its relatively low cost coupled with its physical properties of: low density, high chemical resistance, tensile strength, etc., make it an attractive material for use in the replacement of traditional materials such at aluminum, steel, cotton, wool and other polymers. PP is used in articles from film and fiber extrusions to injection molding applications; it has found its way into materials we utilize every day, from the cars we drive to that packaging our food comes in. As a result, there are many producers and grades of PP available today and therefore, the ability to distinguish one material from another has commercial and technical value.

One challenge is the ability to analyze aesthetic defects where PP is the

polymer. These defects in many cases are appearing streaks, spots, clusters, etc.

which have attracted names such as tiger striping, coffee , and star burst to name

a few. Observing these defects using optical methods has lead to several issues.

1 Due to the fact the molded articles are generally curved and in many cases

quite large, i.e. door panels, the general technique is to cut out the defect in order to apply

an optical method. Since PP is susceptible to stress whitening, many times the defect is

obscured and may be destroyed during sample preparation. The ability to use non-optical

methods to evaluate a defect area is of value due to retention of the visual appearance no

longer being necessary. Additionally, since these defects vary in thickness the ability to cut away by various methods becomes of value. Finally, due to the relaxation characteristics of molded articles, sometimes the defect area changes over time and renders optical evaluation ineffective. Mass spectrometry becomes an attractive method since its sensitivity and method of operation allow it to look at a sample that is only a few microns thick, and the visual characteristics are no longer relevant for interpretation. The major task is to determine if there is a chemical difference between the defect area and the non-defect bulk. Having a method to distinguish between a chemical difference and/or a mechanical defect helps to save time, labor and associated material costs in the course of eliminating these defects thus providing a valuable tool to the polymer manufacturing industry. As a first step in the search for such a method, this thesis examines if PP can be easily and accurately identified utilizing mild pyrolysis and mass spectrometry.

While the use of mass spectrometry techniques has been utilized for the

analysis and characterization of synthetic polymers, certain types of polymers are not

amenable to MS analysis because MS techniques are inherently unsuitable for their

characterization. However, with the use of pyrolysis such limitations can be challenged.

Combining pyrolysis with mass spectrometry to examine structural characteristics of

2 these types of polymers has been performed for some time.2,3,4,5 However, matrix assisted desorption ionization time of flight mass spectrometry “MALDI-TOF MS” has not been widely applied due to the saturated nature of polyolefins. MALDI-TOF MS provides a fast analysis technique fro the identification of the base polymer as well as any additives used in the manufacture of both the polymer and the final article as well.

Since polyolefins are generally saturated hydrocarbons, we need to perform a manipulation in order to make them ionizable by MALDI. Mild thermal degradation over a set temperature gradient will be used for this purpose. Pyrolysis is the application of thermal in the absence of air to produce chemical and physical changes to the base material. Under these conditions, commonly free radical degradation takes place which leads to predictable and ionizable terminal groups.4 The analysis derived from mild pyrolysis and MALDI-TOF MS is discussed in chapter IV.

Chapter II discusses the limited body of work reported about PP analysis by mass spectrometry techniques. Chapter III describes the sample preparation and operation procedures for MALDI-TOF MS. Chapter IV details the results, discussion and potential future work for this set of experiments and finally, chapter V summarizes the findings of this thesis.

3 CHAPTER II

LITERATURE REVIEW

2.1 Introduction

MALDI-TOF MS has not been employed in the analysis of unmodified or nonfunctionalized olefinic polymers due to their saturated nature. As will be shown in this concise literature review, olefinic polymers have been analyzed by pyrolysis and mass spectrometry, utilizing ionization methods other than MALDI. Additionally, there are many articles available which discuss the use of MALDI, coupled with various mass spectrometry detection methods, for the purpose of analyzing synthetic polymers as a general class.5,6,7 However, it is not the goal of this thesis to describe general MALDI applications to synthetic polymer analysis, but rather to focus on those mass spectrometry studies which relate to the identification and characterization of PP. At the time of writing this thesis no direct reference to work utilizing MALDI-TOF MS for the analysis of homopolymer PP could be found.

4 2.2 Ionization Sources

Several appropriate texts have been published which provide a detailed

description of these the ionization techniques that have been utilized with mass

spectrometry analysis, as a result, only a brief description will be provided here.2,3,8

Three main ionization sources have been utilized for the analysis of PP in past work. The first, ionization “EI” involves the ionization of the polymer sample by a beam of

, usually at a potential of 70 eV. The second, field ionization “FI” involves the

removal of an electron from the polymer sample by utilizing an intense .

Finally, “CI” involves the production of ions by reacting the polymer

sample with another molecule which was previously excited or with an ion: M

+ A* → MA+ + e- or M + B+• → M+• + B.3 These three techniques were the most

mentioned ionization sources for past work involving polyolefins but especially PP. This pointed to an opportunity to utilize the proposed method of MALDI as a new approach to the identification and characterization of PP by MS.

2.3 Direct Pyrolysis Analysis of PP

Pyrolysis of PP has been studied for many years and the use of pyrolysis

techniques to assist in the analysis of synthetic polymers has also been employed for

some time; as a result, pyrolysis-mass spectrometry applications have been examined by

various investigators. Several relevant articles relating these techniques to polyolefin

analysis have been reviewed since the mid-1990’s.4,5,9 These articles illuminated the

5 opportunity for the utilization of pyrolysis in conjunction with MALDI-TOF MS for the

identification and characterization of PP.

Previous work on PP employed EI-MS, CI-MS and FI-MS.4,5,9 Previous work on

other polymers documented the usefulness of low temperature or mild pyrolysis,

generally below 400ºC. This past work, which revealed potentially useful techniques for

the analysis and compositional identification of PP and relevant additives, required the

use of direct pyrolysis techniques. Fortunately, several texts have been published which

provide detailed descriptions of direct pyrolysis.10,11 This literature coupled with reported

MS/MS measurements, provided guidelines on how to identify pyrolysis products of PP above 1000 Da as well as organic additives commonly utilized on the production of PP

articles.

2.4 Free Radical Degradation

Several experimental and modeling studies have been published about the

free radical degradation mechanisms of PP and the structures of pyrolysis products

resulting from such degradation.1,4,5,9,12,13 All work relies on the accepted theory that

pyrolysis initiates a free radical degradation9 via “intermolecular abstraction, midchain β-scission, end-chain β-scission, intramolecular hydrogen transfer, radical

addition, bond fission, radical recombination and disproportionation”12. While many of

these will result in fragments which are isomers, it is important to recognize that they all

can occur.

6 Lattimer’s work on PP’s thermal degradation mechanism resulted in a

proposed nomenclature which will be used as a reference, but not strictly followed for the

naming convention adapted in this thesis. He designated six series of pyrolysis products as:

A: MW = 42n

B: MW = 42n + 14

C: MW = 42n + 28

D: MW = 42n + 30

E: MW = 42n + 12

F: MW = 42n + 40

It is important to note that FI mass spectrometry was used to detect these series and other

methods may or may not observe the same results.9 The paper also describes the mass

ranges in which these series are dominant or absent. The schemes described, while not

unique to this paper, were depicted in a concise manner which allowed for ease of

understanding and comparison to other published mechanisms.

Lattimer’s schemes adequately explain the results obtained in this study.

They will be discussed in detail when there results are presented, together with any

deviations observed (see chapter IV). Overall, the reported data were most relevant to the

work described in this thesis and significantly facilitated data interpretation.

7 2.5 Types of Polypropylene

Polypropylene is a polymer where the repeating unit is the propylene monomer.

The three main conformations of the polymer are isotactic, syndiotatic and atactic, see

figure 2.1.1,14 Isotactic refers to the methyl group on the propylene repeat unit always

being on the same side of the chain backbone. Syndiotatic refers to the methyl

group being at alternating sides in a regular pattern along the carbon chain backbone.

Finally, atactic refers to the methyl group being randomly located along the carbon chain

backbone. A PP chain may consist of one or a combination of these three conformations.

The ratio and type of combinations affect not only the but physical

properties as well.

The second descriptor used for PP is amphorous and crystalline.1,14 No polymer

is exclusively amphorous or crystalline, however, PPs are generally referred to as one or

the other. If a polymer is purely amphorous it would have no melting point “Tm” due to a lack of crystals in the polymer matrix and if a polymer were purely crystalline it would have no Tg as a result of having only crystal regions. It is a general rule that atactic

polymers are considered amorphous due to a lack of stereoregularity, which is required

for crystallinity, and are not reported with a Tm, while most crystalline polymers are

reported with both a Tg and a Tm.

8 CH3 CH3 CH3 CH3

H3C CH CH CH CH C C C C CH3 H2 H2 H2 H2 n

isotatic

CH3 CH3 H H H3C C CH C CH C C C C CH3 H2 H2 H2 H2 CH3 CH3 n syndiotatic

CH3 CH3 H H H H3C C C CH C CH

C C C C C CH3 H2 H2 H2 H2 H2 CH3 CH3 CH3 n

atatic

Figure 2.1. Conformations of polypropylene.

9 CHAPTER III

MATERIALS AND METHODS

3.1 Amorphous Polypropylene

The amorphous PP with a number average molecular weight “Mn” of approximately 3700 and a weight average molecular weight “Mw” of approximately

14,000 was purchased from Sigma-Aldrich Company. The polymer is 25% isotactic and

75% atactic and terminated on both ends with a methyl group. The representations of PP appearing in this text are drawn with a regular structure which is not true to its actual conformation, see figure 3.1. The translucent white chunks of polymer were micropulverized cryogenically using a bench top microgranulator at Americhem, Inc.

(Cuyahoga Falls, OH) utilizing carbon dioxide gas. Pulverization was conducted to increase surface area and more easily weigh the microgram portions necessary for mass spectrometry analysis.

CH3 CH3 H2 H2 C C CH3 H3C C C H n H

Figure 3.1. Structure of standard polypropylene demonstrating methyl termination on both ends.

10 3.2 Pyrolysis Procedure

An appropriate milligram amount of polymer, generally between 40 and

80mg, was weighed into an NMR glass tube and then the tube was purged with gas

and flame-sealed. The tubes were placed into a gas oven at the selected

temperature for 30 minutes. Samples were pyrolizied starting at 125ºC up to 300ºC at 25º

increments. All argon purging, flame sealing and pyrolysis were conducted at Noveon,

Inc. (Brecksville, OH) as needed. Once pyrolyzed the samples were left in their sealed

tube until they were selected for analysis. The selected NMR tube was scored with a

glass scorer and carefully broken as close to the sealed tip as possible. This minimized

the amount of broken glass entering into the bottom of the tube where the sample

remained and provided enough room for the to be added.

It is worth noting that not all pyrolyses were done at the same time. In

general, replicates were pyrolyzed together, unless a sample tube broke during flame

sealing or some other unforeseen event in which case a new representative for the lost

replicate was pyrolyzed with other samples. Replicates b and c were pyrolyzed at the

same time, again, unless a sample was lost during preparation for pyrolysis and finally,

replicate d and subsequent additional samples were pyrolyzed as needed.

3.3 Initial Sample Preparation

Initially mass spectrometry sample preparation after pyrolysis was conducted as follows. An appropriate amount of solvent was added to the NMR tube to achieve a

10mg/ml concentration based on the pre-pyrolyzed weight of the sample. In the case of

11 PP the solvent used was chlorobenzene 99.9% HPLC grade. The solvent was purchased from Sigma-Aldrich Company. The NMR tube was then capped and placed on an agitator to facilitate the pyrolyzates going into . The sample and solvent solution

was then transferred to a PP micro centrifuge sample tube. The PP tubes were purchased

through the university chemical stores. The PP tube and the NMR tube were adequately

labeled in case the sample was needed for future analysis. In the case of the PP samples

not all the sample readily dissolved and could not easily be removed from the NMR tube.

The ionizing salt utilized for this study was trifluoroacetate 98% “AgTFA” and the matrix was dithranol which has the following synonyms 1,8,9-anthracenetriol or 1,8- dihydroxy-9(10H)-anthracenone or 1,8-dihydroxyanthrone or anthralin. AgTFA was purchased through Sigma-Aldrich Company and dithranol was purchased through Alfa

Aesear Company. The AgTFA was dissolved in tetrahydrofuran, anhydrous, 99.9%, inhibitor free “THF” to obtain a 10 mg/ml concentration. The dithranol was dissolved in

THF to obtain a 20 mg/ml concentration. The were then mixed in a 10:1:4 ratio

(matrix:salt:sample), by adding the matrix first, then the sample and finally the salt to a

PP sample tube. This sample was again agitated to adequately mix the components. The solution was then spotted onto a MALDI-TOF MS target using ~0.50 μl per spot. A poly(styrene) “PS” Mn ~1900 was utilized as a working external standard. The PS was

dissolved in THF to have a 10 mg/ml concentration. The PS sample was added each time

the target was spotted to calibrate the MALDI-TOF mass spectrometer before each set of

runs. A new sample of matrix and ionizing agent were made at the beginning of the day

a set of experiments were to be analyzed. Old samples of matrix and ionizing agent were

12 not reused after 24 hours. This procedure was utilized until the first set of PP pyrolyzates

was analyzed.

3.3.1 Revised Sample Preparation

The sample preparation after initial analysis differed as follows. The PP

tubes were replaced with glass tubes. Glass was used for storing residual samples from

the NMR tubes and also for mixing samples to be spotted on targets. The mixing ratio

was modified to 7:1:5. Finally, the concentrations of the samples were increased from 10

mg/ml to 30 mg/ml to help increase the S/N ratio.

3.4 Blank Study

The following is the sample preparation for the blank study. Based on the

analysis of the first set of PP samples which will be discussed in chapter IV, it was

determined that a blank study was needed to verify possible sources of contamination.

The screening procedure takes into account all and sample vessels used for this project. The following were each analyzed in both the PP sample tubes and 15 x 45 mm glass vials, see table 3.1 for the mixture study. Several combinations were run for completeness.

13 Table 3.1. Blank study mixture ratios. Sample Name Contents a 100% THF b 100% Chlorobenzene c THF + AgTFA d THF + Dithranol a + b 1:1 b + c 1:1 b + d 1:1 c + d 1:1 b + c + d 1:1:1 e THF + NaTFA

The amounts used were approximately equivalent to the amounts used to make the sample solutions, i.e. 10 mg/ml for AgTFA and NaTFA and 20 mg/ml for the dithranol.

The NaTFA was added in the blank study to the PP tubes only to determine if could be identified as a contaminant in the glass vials. NaTFA was obtained through

Sigma-Aldrich Company.

Later in the study the lab began using 19 x 65 mm glass tubes for sample preparation. When these glass tubes were used, they had to be rinsed with THF prior to sample preparation. This will be discussed in chapter IV. The glass and PP sample tubes were purchased through the university chemical stores; all were made by Fischerbrand.

3.5 Using the MALDI-TOF Mass Spectrometer

A Bruker Reflex III MALDI-TOF mass spectrometer was used to analyze the samples from this study. This instrument utilizes an attenuated laser (337 nm) with a pulse width of approximately 3 nanoseconds. The excitation occurs over a region

14 of 104 μm2 and irradiances are typically in the range of 106 to 107 W/cm2. Figure 3.2 shows a diagram of this reflector-type time-of-flight mass spectrometer.15

Figure 3.2. Diagram of a reflectron MADLI-TOF mass spectrometer.

The ions are created at the after ablation by the laser. They are then accelerated into the field-free region; from there they penetrate the reflector. The purpose of the reflector is to allow ions with the same m/z but different kinetic to exit the reflector at the same time, thus increasing resolution, sensitivity and mass accuracy.

The instrument is equipped with a SCOUT ion source which automates the sample loading and spot selection. The target used consisted of a round stainless steel

15 target with 26 sample positions. A video camera and monitor were utilized to view the

sample being targeted as well as monitoring proper loading and unloading of the target.15

An ion deflector is used to deflect low mass ions and increase the sensitivity for higher mass ions by avoiding saturation effects at the detector. The low mass ions generally originate from the matrix, a contamination, or an irrelevant sample which is lower in mass than the area of interest. Ion detection is based on the fast measurement of an which drops over a 50 Ω resistor as a result of ion impact. The instrument utilized a dual microchannel plate detector “MCP-detector”. It consists of an array of fused lead glass tubes which are cut at a bias angle and machined to an optical finish. The wafers are chemically processed to create a uniform porous structure referred to as microchannels. The microchannels act as electron multipliers with gains of 106 possible. The reflector is a two-stage gridless reflector. The lack of grids allows for an increase in ion transmission and resolution. Data acquisition and instrument control are managed by a UNIX SUN work station.15

3.5.1 MALDI-TOF MS Instrument Conditions

The instrument was run in reflectron mode at +20 kV setting for all

experiments. The time delay varied between 1.00 and 2.00 ns depending on the mass

range of interest. The laser attenuation varied between 28% and 18% depending on the

concentration of the sample and signal to noise ratio of the sample being evaluated. For a

given day and set of experiments the attenuation was optimized and held constant for that

time period. The optimum setting changed over long time periods due to machine

16 variability and modification of sample preparation during the course of this study. The

mass range scanned was approximately 700 to 5000 Da for the PP samples. A set of

samples were analyzed using a low mass cut off of 1000 Da to minimize matrix clusters

and increase the S/N ratio. Between 400 and 1000 laser shots were collected per sample, again depending on the S/N ratio observed during the run.

3.6 Oxygen Contamination Verification

A small series of experiments were conducted to determine whether any

oxidation was occurring during pyrolysis, as will be discussed in chapter IV. These tests

were conducted using only the 250ºC through 300ºC temperatures and the ionizing salt

was changed from AgTFA to either NaTFA or LiTFA. The PP samples were made using

a 30 mg/ml concentration. The NaTFA and LiTFA solutions were made to have a 10

mg/ml concentration utilizing THF as the solvent. In addition to looking at samples

which were pyrolyzed as previously described, a sample which was allowed to degrade in

an open NMR tube was also investigated.

3.7 Data Interpretation

The spectra were interpreted using both monoisotopic and average mass

values for the monomers and ions of interest. Monoisotopic values were preferred but as

higher values were evaluated it became increasingly difficult to identify the C12 peak and therefore the average value for the cluster was utilized to determine

17 peak composition. Table 3.2 lists both the monoisotopic as well as the average mass values for the monomers and ions utilized for this study. Only singly charged ions were observed. Thus, mass (monoisotopic or average) and mass-to-charge ratio (m/z) of these ions have identical numerical quantities.

Table 3.2. Monoisotopic and average masses used for analysis. Substance Mass (Da) Monoisotopic Mass (Da) Average Ag(107)+ 106.9051 107.8682 Ag(109)+ 108.9047 107.8682 Na+ 22.9898 22.9898 Li+ 6.9410 7.0160 C3H6 – PP repeat 42.0470 42.0806 C12 12.0000 12.0110 H1 1.0078 1.0079 O16 15.9949 15.9994

18 CHAPTER IV

RESULTS AND DISCUSSION

4.1 Description of Structures

The mechanisms leading to the observed pyrolysis products are similar to those

referred to in the literature review and will be discussed later. However, in order to facilitate the interpretation of the mass spectra to be shown, it is important to first show the structures proposed to arrive upon pyrolysis and their respective designations, which will be used in the tables and figures to follow. Table 4.1 and Figure 4.1 give a representative example for each of the proposed structures, while all isomers are available in appendix A. The ions observed in the mass spectra of the PP pyrolyzates are

Ag+ adducts. The end group mass of such ions is calculated via the equation m =

42.047n + x + 106.9051 where m is the experimentally measured mass of the ions

(monoisotopic), 42.047n is the mass of the mer being evaluated, x is the mass in Daltons for the end groups and 106.9051 is the mass of Ag107. The equation given applies to

resolved isotopic patterns, from which monoisotopic masses can be extracted. If this is

impossible, an analogous equation with average masses (see table 3.2) must be used.

19 Table 4.1.Mass designations for fragmentation structures. Structure Nominal mass of End Groups (Daltons) A 14 or 56 B 28 or 70 C 0 or 42 P 40 or 82

Ag+ Ag+ H H H2 2 C C CH H2C C CH3 3 C CH HC CH CH n n CH CH CH CH3 CH3 3 3 3

A C

Ag+ Ag+ H H2 H2 H C C CH3 H2C C C CH CH H2C C CH CH n n CH3 CH3 CH3 CH3 CH3

B P

Figure 4.1. Representative structures of PP pyrolyzates.

20 4.2 Blank Study

A blank study was conducted to determine if the sample preparation

procedures used initially in this study were contributing to the observed MALDI mass spectra. A non-pyrolyzed PP yielded no observable peaks at any laser attenuation setting.

From this result it was concluded that the standard sample preparation methods utilized to

analyze the pyrolysis products as described in section 3.1 did not produce any

contaminating and misleading signals. On the other hand, the pyrolyzed PP repeatedly

led to a series of peaks which appeared at the same m/z values independent of the

pyrolysis temperature. This peak series included some but not all expected PP pyrolysis

products, which raised a question as to the source and composition of these peaks.

A further blank study was therefore developed to look at the effects of

pyrolysis product sample preparation upon the observed spectra. Measurements were

conducted in both PP sample tubes as well as 15 x 45 mm glass sample tubes. These

experiments showed that blank samples prepared using PP tubes containing chlorobenzene, THF, AgTFA and dithranol resulted in mass spectra which were similar with the lower mass regions, between 700 and 1100 Da, of the mass spectra created from the pyrolyzed samples. This provided evidence that something besides the PP pyrolyzates was capable of contributing to the spectrum. Conversely, the blanks made utilizing the 15 x 45 mm glass tubes resulted in no observable spectra at any laser attenuation. Therefore, from that point forward all sample preparation was conducted using the glass tubes only. The only potential source of external PP at that point, other than the sample itself, was the Eppendorf pipette tips. However, due to the short time

21 solvents were in contact with the pipette tips, this step did not contribute detectable

amounts of PP to mixtures.

The described results suggest that lower mass PP oligomers and other

molding formulation components were dissolved from the PP sample tubes with the

solvents used in this study. Due to the sensitivity of the mass spectrometer, those

components were detected in the spectra. Without the ability to know the exact

composition of the PP sample tube, i.e. Mn of the polymer, additives, process conditions,

etc., it is very difficult to identify all the observed peaks, which additionally is outside the

scope of this project.

When comparing the PP peaks from the blank study, samples prepared in PP

tubes, and samples prepared in glass, many of the peaks in the lower mass range appear under all conditions. This is illustrated in figure 4.2 which compares the m/z 1000–1100

regions of the spectra of the blank versus those of PP pyrolyzate samples prepared in PP

or glass vials. The m/z 1000-1100 region contains the most reproducible set of oligomer

ions regardless of preparation method. Blank, which is the bottom trace, represents the

spectrum of a sample which contained all preparation materials except the amorphorous

PP. Glass, which is the middle trace, represents the spectrum obtained from PP

pyrolyzates using glass vials only for sample preparation. Finally, PP tube, which is the

top trace, represents a spectrum obtained from a pyrolyzed PP sample contained in a PP

centrifuge tube. See table 4.2 for a list of the common peaks. It can be seen that 100% of

the peaks observed from the blank sample appear in the mass spectra obtained from PP

actual pyrolyzates, prepared either in PP or glass tubes.

22 Table 4.2. List of common peaks: blank compared to samples prepared via different protocols.

PP Tube Sample Glass Sample Prep Prep PP Blank PP Blank End Group Average Mass Designation x x 794 A x x 808 B x x 1004 A x x 1018 B x x 1032 C x x 1046 A x x 1060 B

These experiments emphasize the need for blank analysis, to ensure that the

sample preparation procedure used does not contaminate the samples to be analyzed. The

high sensitivity of MS allows the detection of minute background amounts, which must

be elucidated prior to the actual sample analysis in order to avoid systematic errors.

4.2.1 Alternative Glass Vials

It was discovered that when the 15 x 45 mm glass tubes were replaced with

19 x 65 mm glass tubes a new contaminant was observed. Upon rinsing the 19 x 65 mm

tube with THF and adding AgTFA and dithranol, a spectrum with a 74 Da repeat unit

was obtained. This is consistent with a siloxane polymer, see figure 4.3. It is theorized

the residual polysiloxane likely originated from a mold release agent used by the glass

manufacturer. Once this contamination was discovered, the 19 x 65 mm glass tubes were

rinsed with THF prior to sample preparation to remove the residual contaminant.

23

24

Figure 4.2. Comparison of blank (contained in a PP tube) to PP pyrolyzate samples prepared in PP or glass vials. Only the m/z 1000-1100 region of the corresponding MALDI-TOF mass spectra is displayed.

5000

4800

4600

4400

4200

4000

3800

3600

74 3400

3200 m/z

74 3000

2800 74 2600

74 2400

2200

74 2000

1800

74 1600

1400 Figure 4.3. MALDI-TOF mass spectrum of the polysiloxane contaminant from 19 x 65 mm glass tubes.

0% 0.0 0.00% 50.00%

10 % %

25 4.2.2 Blank Results

One theory as to why these contaminates are observed when analyzing a

polyolefin but not other types of polymers is differences in ionization efficiencies. It is

possible that lower molecular weight PP extracted from the centrifuge sample tubes and

the polysiloxane extracted from the glass sample tube have higher MALDI efficiency and therefore are more readily observed during MALDI-TOF analysis versus the mild

pyrolysis products from the amphorous PP. Another possibility is that higher

concentrations are attained with the contaminants than the PP pyrolyzates. Regardless of

where these contaminants come from, they illustrate the sensitivity of MALDI-TOF MS

as well as the need to be vigilant in sample preparation techniques. Additionally, this demonstrates the need to classify as many potential sources of contamination and catalog as many of them as possible in order to increase the probability of correctly identifying the material(s) of interest.18

4.3 PP Individual Temperature Analysis-Introduction

An amorphous PP of low Mn was selected for this study. This PP proved to

be easy to weigh and transfer into the NMR tubes after micro-pulverization, which in turn

allowed for fast and efficient sample preparation for the replicate samples analyzed in

this study.

The first step in this study was to verify the theory that a saturated polymer

should not provide an observable spectrum under MALDI-TOF MS conditions. For this,

an unpyrolyzed sample of the PP was prepared and evaluated. Dithranol and AgTFA

26 were used as the matrix and cationizing salt respectively. As expected, this material provided no observable PP peaks at any laser attenuation. This is a result of PP’s saturated structure, which lacks a basic site at which Ag+ can attach. From this point forward pyrolysis was conducted prior to any mass spectrometry evaluations. The purpose of pyrolysis was to create, via free radical reactions truncated PP chains containing one or more double bonds that could then be silverated and observed under

MALDI-TOF MS conditions. The pyrolysis degradation products of PP, as previously stated, are well documented. This study aimed not at reinforcing or questioning the literature results but rather at determining if a commercial PP could be characterized under MALDI-TOF MS conditions. The literature results provided a guide to identify the pyrolysis products and thus confirm whether they can be used to characterize a commercial PP by this technique.

The initial set of experiments was to evaluate PP pyrolysis products over a temperature gradient from 125ºC through 300ºC at 25ºC increments. The assumption was that mild pyrolysis would limit the fragmentation and decrease the complexity of the spectra. An additional goal was to observe how far out in mass the PP fragments could be observed. Finally, replication was conducted to verify if the results could be reproduced and to see what observations could be made when comparing the replicate data, i.e. is one oligomer series (within the pyrolysis products) most abundant over all temperatures and masses or does its yield change with temperature or mass range as seen in previous work? What changes occur over the temperature range, does fragmentation increase, decrease? Each temperature is discussed individually and then the data are evaluated as a whole.

27 4.3.1 PP Analysis – 125ºC

125ºC was the lowest pyrolysis temperature examined in this study. While

this is below the softening point “Tg” of the PP used (Tg ~ 155ºC) it was still sufficient to

cause hemolytic cleavages and create radicals under the conditions previously described, which ultimately yielded the products observed in the mass spectra. Radical formation at this low temperature is probably due to residual peroxides, monomers, oligomers and/or catalyst present in typical commercially produced polymers. Three replicates (a, b, c) were pyrolyzed and processed under the original conditions of 10:1:4

(matrix:salt:sample) and sample concentration of 10 mg/ml and a fourth replicate (d) was pyrolyzed and processed under the revised conditions of 7:1:5 and sample concentration of 30 mg/ml.

Replicate a yielded no definitive PP isotope clusters with the peaks observed appearing to arise from the matrix, silver clusters or contamination from the PP centrifuge tubes, see figure 4.4. This may be due to the limited solubility of the PP pyrolysis products in chlorobenzene at room temperature and their concentration from this sample being to low to be observed under the MALDI-TOF MS conditions selected for these experiments. It may also be due to replicate a being a failed sample, because it did not receive enough thermal energy to create radicals.

Replicates b and c yielded PP isotope clusters from 768 Da to 1256 Da, see figures 4.5 and 4.6. Many of the observed clusters are common to the blank; see table

4.3, where underlined and italicized masses indicate that these ions were observed in the blank; however, the real samples gave more abundant ions than the blank and, hence, must have contained PP products from the pyrolyzed PP sample not just the centrifuge

28 tubes. Tables of this type will be used throughout the thesis to help describe the

experimental observations. However, only table 4.3 appears in the body of the text, all

other similar tables are grouped in appendix B. It is important to note that this data was

gathered from spectra acquired using 700 Da as the cut-off mass. Not included in the

tables are peaks > m/z 700 which are believed to originate from a combination of the

following sources: silver clusters, matrix interference and residual products from the PP centrifuge tubes. Ions were assigned to latter groups based on their isotopic patterns,

intensities and/or lack of resolution within the isotopic clusters. No smoothing was used

to interpret the data so as not to discriminate against PP isotopic clusters that are near the

noise level. While it was not conclusive whether the pyrolyzed PP was contaminated

with PP oligomers from the centrifuge tubes, the mass spectra provided enough evidence

to conclude that thermal degradation at 125ºC temperature was capable of creating

radicals from the amphorous PP which gave rise to detectable products that were

indicative of the material of interest.

Replicate d helped to reinforce these observations since no PP centrifuge

tubes were used during this sample preparation. In general, the mass spectrum replicate d did not correlate to those of replicates b and c as well as the spectra of b and c did to each other. Approximately 80% of the identified products from replicates b and c correlate to each other where as only approximately 40% of the identified from d correlate to those from replicates b and c. This could be due to many factors. First, replicates b and c were pyrolyzed at the same time; replicate d for this temperature were pyrolyzed at a later date.

The matrix:AgTFA:sample mixing ratio used for b and c differed from that of d vida supra. Finally, the sample concentration in d was 30 mg/ml whereas in b and c it was 10

29 mg/ml. The important observation is that products of the same mass that are present in

the spectrum of d as well as the spectra of b and c have identical isotopic patterns and

quite similar relative intensities. Thus, all three pyrolyses must have created similar

hemolytic cleavages, leading to analogous product compositions.

This is further evidenced by the normalized data used to compare the

replicates. While several pyrolysis products have larger relative abundances in d versus b

and c, this does not hold true for all observed isotope clusters, see table 4.4. This table compares the peak intensities of the three replicates using standardization function,

STANDARDIZE, as found in Microsoft Excel. The goal of performing this comparison was to assess which end groups had the highest abundance, so that qualitative statements could be made about the preferred degradation pathways of PP. Since 125ºC was the lowest temperature used for pyrolysis, the dominant product(s) formed at this temperature reveal the lowest energy thermal degradation pathway. According to figures 4.5-4.7 and table 4.4, structure A appears to be the dominant product at 125ºC. When the free radical degradation mechanism is reviewed for this polymer, it will be shown that short PP chains of structure A can be derived from more pathways than any other structures, see section 4.5 for the precise mechanisms and descriptions.

Lower mass sodiated oligomers were observed with replicate d. The Na+ ions are supplied by the glass vials used for sample preparation for the replicate d. The increased sample concentration may have contributed to the observance of these peaks as well. The masses of the Na+ containing ions observed are given in table 4.5. Note that

sodiated ions are readily distinguished from silverated ions based on their isotopic

patterns. For both sodiated and silverated products, relative abundances decrease in the

30 order A>B>C. The peaks at m/z 881, 896, 910 and 1121 in figure 4.7 (marked ?) could not be interpreted; they have end mass results that are not easily correlated to a PP fragment and their source is uncertain.

Finally, a single factor ANOVA was conducted to determine if the replicate spectra were statistically equivalent or not. The results show that for both the complete list of C12 peaks identified and the list of C12 peaks the three replicates had in common there was no statistical difference for the intensities in the three replicate spectra. The intensities were taken from the data which was interpreted using the Genomics Solutions freeware version of M over Z software. See table 4.6 for the ANOVA results of the common C12 peak list at 125ºC. For the remaining temperatures, the ANOVA tables are in appendix C.

31 Table 4.3. Comparison of the MALDI-TOF mass spectra of the pyrolyzates (125ºC) from replicate samples b, c and d. Only ions above m/z 700 cutoff mass) were recorded. An x indicates that this ion is observed. The masses listed are nomibal monoisotopic values. replicate samples b c d End Group 778 x P 780 x C 794 x x x A 808 x x x B 822 x C 836 x A 947 x x x C 1004 x x x A 1018 x x x B 1032 x x x C 1046 x x x A 1060 x x x B 1073 x x C 1157 x C 1199 x C 1228 x x B 1242 x x x C 1256 x A

32

Table 4.4. Comparison of the MALDI-TOF mass spectra of the pyrolyzates from samples b, c and d (125ºC) using normalized abundances. Replicate samples Mass b c d End Group Mer 778 0.066 P 16 780 1.079 C 16 794 0.138 -0.246 4.693 A 16 808 -0.100 -0.270 2.176 B 17 822 -0.122 C 17 836 -0.585 A 17 947 0.010 0.164 -0.640 C 20 1004 0.845 0.853 -0.503 A 21 1018 0.461 0.352 -0.642 B 22 1032 0.460 0.178 -0.568 C 22 1046 0.235 -0.193 -0.706 A 22 1060 -0.076 -0.399 -0.778 B 23 1073 -0.434 -0.429 C 23 1157 -0.429 C 25 1199 -0.723 C 26 1228 -0.662 -0.565 B 27 1242 -0.502 -0.448 -0.963 C 27 1256 -0.725 A 27

33 Table 4.5. Sodiated ions (nominal monoisotopic mass) in the MALDI mass spectrum of sample d, pyrolyzed at 125ºC.

Mass (Da) End Group 710 A 724 B 738 C 934 B 948 C 962 A 976 B

Table 4.6. ANOVA results for common C12 peaks in the MALDI-TOF mass spectra of replicates b, c and d. SUMMARY Groups Count Sum Average Variance b intensity 9 14289 1588 214329 c intensity 9 12549 1394 249060 d intensity 9 14992 1666 5137009

ANOVA Source of Variation SS df MS F P-value F crit Between Groups 351484 2 175742 0.094 0.910 3.403 Within Groups 44803184 24 1866799

Total 45154667 26

34

1400

945

The inset shows an expanded 920 1200 m/z

895 m/z

sample a, pyrolyzed at 125ºC.

870 1000 0%

50%

100%

% %

Figure 4.4. MALDI-TOF mass spectrum of view of the m/z 870-960 region spectrum. 800 0%

50%

100%

% %

35

1100

1600

C

B

1050 A

The inset shows an expanded C

m/ z B

1300 A A C 1000 B C m/z matrix

+

Ag

C B A 950 C 0% B

50%

100%

A

% % 1000

C

B A

Figure 4.5. MALDI-TOF mass spectrum of sample b, pyrolyzed at 125ºC. view of the m/z 950-1100 region. 700 0%

50%

100%

% %

36

1100

1600

C

B

A 1050

C

m/z The inset shows an expanded view B

A 1300

1000 C

B

matrix m/z

C + Ag

sample c, pyrolyzed at 125ºC. 950 C B

0% A 50%

100%

C % % B A 1000

C

B A

Figure 4.6. MALDI-TOF mass spectrum of of the m/z 950-1100 region. 700 0%

50%

100% % %

37

1200

C

?

1100 B m/z Na A C inset shows an expanded view of

C B

Na B A 1000 Na

A m/z 705 715 725 735 745 755 765 775 785 0%

50%

100%

% %

? ? 900

sample d, pyrolyzed at 125ºC. The ? ains sodiated pyrolysis products.

A C

B 800 A C

Na

C Na B

Na A Figure 4.7. MALDI-TOF mass spectrum of the m/z 700-790 region, which also cont 700 0%

50%

100% %

%

38 4.3.2 PP Analysis – 150ºC.

150ºC was the second temperature that the PP samples were exposed to. This temperature is approximately at the Tg for the PP utilized in this study. Replicate a for

this temperature was the first pyrolyzed PP sample subjected to MALDI-TOF MS. The

results (figure 4.8) were very encouraging and the project proceeded to look at higher

temperatures. However, the repeat pattern observed from the first sample set at 150ºC,

225ºC, 250ºC and 275ºC (the higher temperatures will be discussed later) could not be reproduced again. It is unknown at this time why that occurred. Replicates b, c and d will be compared in more detail, as they are similar with each other but moderately different from replicate a.

As can be seen in figure 4.8 versus figures 4.9-4.11, replicate a yielded a very

different spectrum versus replicates b, c and d. Replicate a provided a spectrum

dominated by silverated PP oligomers with a 42 Da repeat unit out past 3000 Da (average

masses were used past the 2000 Da mass). Structure C was assigned to this dominant

fragment series based on the corresponding peak masses, see appendix B, table B1 for

full peak list. There was some similarity between replicate a and the others in the lower mass region which contained common peaks with those observed in replicates b, c and d.

No other correlation was observed.

As at 125ºC, replicates b and c had more similar mass spectra than replicate d.

There was an 80+% correlation of monoisotopic (all C12) peaks between b and c and a

70+% correlation between d, b and c. The difference in correlation of monoisotopic

peaks may be linked to the trend of replicate d producing several lower mass ions and

lacking a few higher mass ions that appear in the spectra of the b and c replicates; see

39 appendix B, table B.2 for a full mass table with normalization data for these three

replicates. Based on the normalized ion abundances at this temperature (excluding

replicate a), truncated PP chains with structure A are again the major pyrolysis product.

Fragments with end groups A, B and C appear with approximately equal frequency at

this temperature. Single factor ANOVA showed no statistical difference in the relative

intensities of the mass spectra of replicates b, c and d; this was true for the monoisotopic

peaks the three replicates shared in common as well as for the complete list of

monoisotopic peaks identified. This revealed that replicates b, c and d lead to reproducible results; see appendix C table C.1 for ANOVA results. It can further be

concluded then that pyrolysis creates PP fragments at this temperature that can be used

for the characterization or classification of the original PP sample.

40

C

42Da

e inset shows an expanded view of

m/z C

m/z

42Da

sample a, pyrolyzed at 150ºC. Th

C

985 995 1005 1015 1025 1035 1045 1055 1065 1075 0%

50%

100%

% %

Figure 4.8. MALDI-TOF mass spectrum of the m/z 985-1180 region. 700 1000 1300 1600 1900 2200 2500 2800 3100 3400

0%

50%

100% % %

41

1300

A B C

1200 A

m/z e inset shows an expanded view

C

1100

B

A B

C

B

A m/z 1000

A

sample b, pyrolyzed at 150ºC. Th 1000 1010 1020 1030 1040 1050 1060 1070 0%

50%

100% % %

900

B 800 A

Figure 4.9. MALDI-TOF mass spectrum of of the m/z 1000-1070 region. 700 0%

50%

100% % %

42

1300

B C B

1200 A

m/z

C

The inset shows an expanded 1100

B

B A

C B

A m/z 1000

A

1000 1010 1020 1030 1040 1050 1060 1070 0%

50%

100% C % % sample c, pyrolyzed at 150ºC.

900

B A 800

Figure 4.10. MALDI-TOF mass spectrum of view of the m/z 1000-1070 region. 700 0%

50%

100%

% %

43

1300

1200

AB

The inset shows an expanded

1100

m/z

B C

A

C

B

A m/z 1000 B

900

A

1000 1010 1020 1030 1040 1050 1060 1070 0%

50%

100% %

% A

C

B 800 A

C

C B A Figure 4.11. MALDI-TOF mass spectrum of sample d, pyrolyzed at 150ºC. view of the m/z 1000-1070 region. 700

0%

50%

% 100% %

44

4.3.3 PP Analysis – 175ºC

Replicate a yielded no usable data at 175ºC. Replicates b, c and d were prepared

and analyzed as described for the lower temperatures. The results followed similar trends

to those observed at the two previous temperatures. The corresponding spectra are

displayed in figures 4.12-4.14.

The difference seen at this temperature was that replicate b yielded PP fragments

past 1700 Da. Also more fragments could be identified in the spectrum of b at 175ºC

suggesting that fragmentation was increasing from 150ºC to 175ºC. However, replicate d

yielded essentially the same spectra at 150ºC and 175ºC; the S/N was better at 175ºC,

allowing for the detection of a few additional products in the 1200 Da range. The mass

spectrum of replicate c at 150ºC was very similar to those at the previous temperatures.

Due to the observance of the additional peaks for replicate b the correlation between replicates dropped slightly for this temperature versus the previous two. The b and c replicates coordinated ~70%, while d corresponded to the b and c replicates ~43%.

Product A was still the fragment with the highest abundance and product C appeared more frequently especially as the mass increased. Finally, the ANOVA analysis indicated there was no statistical difference between the replicates. This is of interest due to the spectra appearing visually different compared to each other which might lead one

to assume the replicates had little to no correlation. See appendix B, table B.3 and

appendix C table C.2 for the mass table and the ANOVA results, respectively.

45

C

C

B

A

inset shows an expanded view of

B

m/z

? C ?

C

A m/z B

BC C

C A sample b, pyrolyzed at 175ºC. The ?

1000 1010 1020 1030 1040 1050 1060 1070 1080 0% C

50% B

100%

A % % C

B A

C

C

B A

B

Figure 4.12. MALDI-TOF mass spectrum of the m/z 1000-1080 region.

700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800

0% 50%

% 100% %

46

C

B

A

m/z The inset shows an expanded view

C

B A C m/z

B

A sample c, pyrolyzed at 175ºC.

? 1000 1010 1020 1030 1040 1050 1060 1070 1080

0% 50%

C

100% % % B A

C B

A

B A

Figure 4.13. MALDI-TOF mass spectrum of of the m/z 1000-1080 region. 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 0%

50%

100% % %

47

B

inset shows an expanded view of

A

m/z

C

m/z

BCAB

B sample d, pyrolyzed at 175ºC. The

C B

C B

A A

1000 1010 1020 1030 1040 1050 1060 1070 1080

0% 50%

100%

? % %

C

B A

A

C C B A 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 Figure 4.14. MALDI-TOF mass spectrum of the m/z 1000-1080 region.

0%

50%

100% % %

48 4.3.4 PP Analysis – 200ºC.

At this point, replicates a and b had been tested through 300ºC and replicate c through 175ºC. It was at this point that the contribution from the PP centrifuge tubes was discovered. Since not all of the c replicates had been evaluated yet, it was not necessary to create d replicates for 200º - 275ºC to perform all glass sample preparation; therefore, for 200º through 275ºC there is no replicate d. The all glass sample preparation sample will be the c replicate instead. While this reduces the total number of replicates for these temperatures, it should not negatively impact the overall analysis.

Once again replicate a provided no useful spectrum. It was at this point that the sample preparation step was slightly modified to increase the amount of time the PP pyrolyzate material sat in solvent prior to analysis. The time was increased from ~5 to

~30 minutes with 1-3 minutes of agitation during this time period. Due to the loss of the third replicate, statistics were not performed on this temperature. With only one degree of freedom in the calculations any result would be subject to speculation and have minimal to no value, therefore this temperature will be discussed in purely qualitative terms.

The mass spectrum of replicate b was noisy at this temperature and average masses had to be used above 1100 Da. PP fragments were observed out to 2000+ Da, see figure 4.15. The distributions detected followed the fragment pattern observed in previous temperatures, see appendix B table B.4 for mass table which includes replicate c. Due to the poor S/N ratio in figure 4.15, only the insert is labeled.

Replicate c showed a similar spectrum to those observed so far for replicates d

(prepared using all glass sample preparation). Clusters into the 1300 Da range were now

49 identifiable. One difference noted between 200ºC and prior temperatures for this

replicate was the increased abundances of sodiated ions. In fact, most isotopic clusters in

the spectrum of replicate c (figure 4.16) appear to be composite, containing sodiated as

well as silverated PP oligomers. The mass difference between 107Ag and 23Na is 84 Da; hence, the [M + 107Ag]+ adduct of a PP fragment type is isobaric with the [M + 23Na]+

adduct of the same fragment type (A, B or C) plus two more repeat units (+2x42 = +84

Da). Either the glass tube used with this replicate contained more Na+ than usual, and/or

this sample was not doped with sufficient Ag+. Unfortunately, the ions observed were

not abundant enough for MS/MS examination, which would have unveiled compositional

information. Interestingly, the cluster group usually observed between 1000 and 1080 Da

is absent in this sample, see figure 4.16. The reason for this deviation is unknown.

Future work may look at enhanced sample preparation techniques in order to obtain

MS/MS spectra to further examine the trends observed when glass tubes are utilized to prepare the samples.

50

2800

C

2500 B

The inset shows an expanded view A 2200

m/z

C 1900 m/z

B sample b, pyrolyzed at 200ºC.

1600

A

1300 1000 1010 1020 1030 1040 1050 1060 1070 1080 0%

50%

100% %

%

1000

Figure 4.15. MALDI-TOF mass spectrum of of the m/z 1000-1080 region. 700 0%

50% 100% % %

51

B t shows an expanded view

A

m/z C A

C

rolyzed at 200ºC. The inse m/z

B

B A

C B A

875 885 895 905 915 925 935 945 955 965 0%

50%

100% % %

B A C

B A

A C

B A Figure 4.16. MALDI-TOF mass spectrum of sample c, py of the m/z 875-965 region. 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800

0%

50% 100% %

%

52 4.3.5. PP Analysis – 225ºC

The b replicate at this temperature yielded no usable data. As mentioned

previously, replicate a for this temperature was one of the first samples analyzed using PP

tubes. It will be discussed qualitatively as will the c replicate at this temperature. As

stated in section 4.3.1, the type of spectra provided by replicate a could not be

reproduced; therefore, replicate c is assumed to be more representative of the sample

analyzed in this study. With only two replicates to evaluate at this temperature, and one of them being suspect, no ANOVA analysis was performed at 225ºC.

Replicate a provided monoisotopic peaks past 1500 Da with a fairly regular

repeat of the A, B and C structures present for each of the mers. PP fragments

(unresolved isotopic clusters) can be observed past 3000 Da which approaches the Mn of the base polymer, see figure 4.17. The dominant fragment at 225ºC is C, while fragments

A and B have lower relative intensities throughout the mass spectrum. This characteristic was also observed at lower temperatures with replicate sample a (see, for example, figure

4.8). A full mass table for the a and c replicates can be found in appendix B, table B.5.

Replicate c provided a somewhat different spectrum versus previous samples prepared using the modified sample preparation protocol. Approximately 75% of the identified monoisotopic peaks from replicate c appear in the spectrum of replicate a. The sodiated peaks seen in previous samples are absent at this temperature with the only identified sodiated peak appearing at ~892 Da. The number of PP fragments observed increased at this temperature and monoisotopic peaks could be detected into the 1400 Da range. There is fragmentation past this range, but it is impossible to quantitatively separate their higher mass pyrolysis products from the noise without manipulating the

53 data. There were also several peaks that had significantly increased intensity versus the surrounding peaks, see B, BNa, and A in figure 4.18; the reason for this phenomenon is unclear. Replicate c, in contrast to replicate a, provided more PP chains with structure A.

As will be seen in the figures from this point forward, all the peaks will no longer be labeled due to the increased fragmentation taking place at higher temperatures. This makes the spectra difficult to interpret. The common fragment series discussed throughout the thesis will, however, still be identified as well as any other important peaks which bear discussion.

54

2800

C

2500 B

e inset shows an expanded view of A

C 2200

m/z

C

1900 m/ z

B C sample a, pyrolyzed at 225ºC. Th 1600

C

C C C

C C

A C C 1300 C

1000 1010 1020 1030 1040 1050 1060 1070 1080 C

0% C 50%

100%

C % %

C C

+ C 1000

Ag C

C

C C

C

Figure 4.17. MALDI-TOF mass spectrum of the m/z 1000-1080 region. 700

0%

50% % 100% %

55

C

B

e inset shows an expanded view of A

m/z

C

m/z

B

sample c, pyrolyzed at 225ºC. Th

A A

C

B 1000 1010 1020 1030 1040 1050 1060 1070 1080 A 0%

C 50% B

100%

A %

%

Na

B

B

A C

C B

A

C B A Figure 4.18. MALDI-TOF mass spectrum of the m/z 1000-1080 region. 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800

0%

50%

100% % %

56 4.3.6. PP Analysis – 250ºC.

At this temperature all three replicates provided spectra. The data was not normalized

because a statistical difference was found between the relative intensities for this set of

replicates, see appendix B, table B. 6 and appendix C table C. 3 for full mass table and

ANOVA results for common peaks. Of the 108 peaks identified in the mass spectra of the

three replicates, only 34 or ~30% are common to all three. Replicates a and b share ~76% of

their spectral peaks, replicates a and c share ~74% of their spectral peaks, and b and c share

~64% of their spectral peaks. This indicates that while any two replicates appear to correlate well, when all three are taken considered, the replication drops significantly; this was observed in the analysis as well. Due to the increased fragmentation at this temperature only the insets in figures 4.19 – 4.21 were labeled. For the full mass list and fragment assignment refer to table B. 6. Due to the statistical inequality of the replicates, only a qualitative assessment could be made as to which fragment was the most abundant.

Replicate a yielded monoisotopic peaks out to ~1600 Da and unresolved clusters past

2300 Da. Fragments with structures A and C appear at approximately equal frequency in this

spectrum with the B structure generated at nearly ½ the intensity of the A and C structures.

Qualitatively, the C fragment was slightly more abundant in the range of monoisotopic peaks

(low masses), with the A and B fragments being of approximately equal abundance.

Replicate b showed a different trend versus replicate a. Replicate b yielded isotopically

resolved peaks out to ~1400 Da and unresolved peak clusters past 1600 Da. The A fragment

appeared most frequently, with B and C having equal frequency. Qualitatively, the A

fragment is slightly more abundant than the ~equally abundant B and C fragments. For

replicate c monoisotopic peaks are observed to ~1100 Da and unresolved peak clusters out

57 past 1500 Da. Peak identification in the spectrum of the c replicate was hampered by a noisier spectrum as compared to other spectra of this series. With the all glass sample preparation samples, it appears as if each 25ºC increase in pyrolysis temperature expands the mass range of observable fragments by approximately 100 Da. The A, B and C fragments appear with equal frequency, with the A and B fragments being of approximately equal intensity and the C fragment being approximately half the intensity of A.

58

C

B

e inset shows an expanded view of

A

m/z

m/z C

sample a, pyrolyzed at 250ºC. Th

B

A

1000 1010 1020 1030 1040 1050 1060 1070 1080 0%

50%

100%

% %

Figure 4.19. MALDI-TOF mass spectrum of the m/z 1000-1080 region. 700 1000 1300 1600 1900 2200 2500 2800

0% 50%

100% %

%

59

C 2800

B

2500

inset shows an expanded view of

A 2200

m/z

C

1900 m/z B

sample b, pyrolyzed at 250ºC. The

1600

A 1000 1010 1020 1030 1040 1050 1060 1070 1080

0%

50%

100% % % 1300

1000

Figure 4.20. MALDI-TOF mass spectrum of the m/z 1000-1080 region. 700 0%

50%

100% %

%

60

2800

C

2500

B

The inset shows an expanded view 2200

A

m/z

1900 m/z C

sample c, pyrolyzed at 250ºC. 1600

B

1300

A 1000 1010 1020 1030 1040 1050 1060 1070 1080

0% 50%

100%

% %

1000

Figure 4.21. MALDI-TOF mass spectrum of of the m/z 1000-1080 region. 700 0%

50%

100% %

%

61 4.3.7. PP Analysis – 275ºC

At this temperature all three replicates yielded spectra (figures 4.21-4.23). Replicates

a and b gave statistically equivalent mass spectra. The spectrum of replicate c was not

statistically equivalent to those of a or b, see table C.4 for ANOVA table for the three

replicates. Additional ANOVA analysis to show that a and b were equivalent and that c was

not equivalent to either was not performed. A total of 138 peaks could be identified at this

temperature, 135 of which were present in the spectra of replicates a or b and 3 of which

were only present in the spectrum of c. The three replicates shared 8 common peaks at this

temperature. This is primarily the result of replicate c contributing only 19 peaks. Replicates

a and b share ~50% of their observed peaks. Replicate c has a little over 50% similarity to a

or b. Overall, A, B and C fragments appear at approximately equal amounts. The

statistically equivalent replicates a and b led to fragment intensities that were highest for

structure C, slightly smaller for structure A, and smallest for B (approximately half the

abundance of A or C).

Replicate a yielded the most observed peaks at this temperature. Monoisotopic all-12C

peaks were observed out to 1700 Da and using unresolved PP clusters out past 2800 Da, see

table B.7 for complete mass table. Replicate b yielded 84 PP fragments, 38 of which gave

monoisotopic peaks and the remaining unresolved peak clusters. Replicate b yielded ions out

past 2300 Da. Replicate c yielded the least number of peaks at this temperature. All-12C monoisotopic peaks were observed out to 1500 Da. Most notable for this replicate was the absence of the set of peaks between 1000 and 1100 Da. For replicate c the A fragment is dominating based on abundances. Due to the increased fragmentation observed from replicates a and b, only the insets were in figure 4.22 and 4.23.

62

2800

C

2500

B

e inset shows an expanded view of

2200 A

m/z

1900 m/z C

sample a, pyrolyzed at 275ºC. Th

1600 B

1300 A 1000 1010 1020 1030 1040 1050 1060 1070 1080

0% 50%

100% %

% 1000

Figure 4.22. MALDI-TOF mass spectrum of the m/z 1000-1080 region. 700 0%

50%

100% %

%

63

2800

C

2500 B

The inset shows an expanded view A 2200

m/z

C 1900 m/z

B sample b, pyrolyzed at 275ºC.

1600

A 1000 1010 1020 1030 1040 1050 1060 1070 1080 1300 0%

50% 100% % %

1000

Figure 4.23. MALDI-TOF mass spectrum of of the m/z 1000-1080 region. 700

0%

50%

% 100% %

64

950 B

B

A

e inset shows an expanded view of C B A m/z C C 910

Na B

m/z C B

A C Na A B sample c, pyrolyzed at 275ºC. Th

870 0%

50%

100% % % B

A C Na B Na

A

A C

B A Figure 4.24. MALDI-TOF mass spectrum of the m/z 870-960 region.

700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 0%

50% % 100% %

65 4.3.8. PP Analysis – 300ºC.

At 300º the replicates were designated as a, b and d. All three replicates yielded

spectra for analysis. There was no statistical similarity between any of the replicates

intensities at this temperature, see table C.5. The three replicates had 10 common peaks out

of 76 total observed peaks, see table B.8 for complete mass table. Replicates a and b had

only 23% of their peaks in common, while replicate d shared less than 20% of its peaks with

a or b. This temperature had the lowest correlation of all temperatures. The A and C fragments appeared at equal frequencies with the B fragment being only slightly less frequent. For replicate a, the C fragment was slightly more abundant, while for the b and d replicates the A fragment was the most abundant. In all cases the B fragment was the least

abundant.

Replicate a in this case yielded the fewest peaks, with monoisotopic peaks being

identified out to 1284 Da and unresolved peak clusters out to ~1700 Da. Replicate b

provided the most peaks, with monoisotopic peaks being observed out to 1464 Da and

unresolved clusters out to ~1900 Da. Replicate d yielded monoisotopic peaks to 1087 Da

and unresolved clusters out to 1422 Da. The trend of being able to see ions farther out into

the mass range as temperature increases appears to have reversed at 300ºC compare figures

4.25 – 4.27 to figures 4.19-4.23. Unlike at 275ºC all three replicates yielded peaks in the

mass range of 1000 – 1100 Da. Again, due to the low S/N and increased fragmentation, only

the insets are labeled. Section 4.5 will discuss in more detail the results at the higher

temperatures.

66

2800 2800

C

2500 2500 B

e inset shows an expanded view of 2200 2200 A

m/z

C 1900 1900 m/z m/z

B sample a, pyrolyzed at 300ºC. Th 1600 1600

A

1000 1010 1020 1030 1040 1050 1060 1070 1080 0% 1300 1300 50%

100% % %

1000 1000

Figure 4.25. MALDI-TOF mass spectrum of the m/z 1000-1080 region 700 700

0% 0%

50% 10 %

%

67

2800

C

B 2500

inset shows an expanded view of 2200

m/z

CA

1900 m/z

B

1600 sample b, pyrolyzed at 300ºC. The A

1000 1010 1020 1030 1040 1050 1060 1070 1080 0%

50%

100% % % 1300

licate b with 1000 – 1080Da inset. ion.

p g

1000

ure 4.26. 300ºC re g the m/z 1000-1080 re Figure 4.26. MALDI-TOF mass spectrum of Fi 700

0%

50% 100% %

%

68

2800

C

2500 B

set shows an expanded view of the

2200 A

m/z

C 1900

m/z

B mple d, pyrolyzed at 300ºC. The in

1600

A

1000 1010 1020 1030 1040 1050 1060 1070 1080 0% 1300

50% 100% %

%

1000

Figure 4.27 MALDI-TOF mass spectrum of sa m/z 1000-1080 region.

700

0%

50% 100% %

%

69 4.4. Additional PP Analysis

In addition to the data previously discussed, two other approaches were investigated

to better understand the performance of pyrolysis-mass spectrometry. First, due to the large

number of fragments observed, especially at the higher temperatures, and the interference

from the matrix, the cut off mass was increased to 1200 Da for a series of samples from

175ºC through 300ºC. This was expected to increase the intensity of the higher mass peaks

and thus render a better picture for how far out on the mass scale the PP fragments could be

observed. Second, to test for the possible interference of oxygen, several pyrolyzates were

analyzed using NaTFA and LiTFA as the MALDI ionization agent (instead of AgTFA), in

order to determine if oxygenated products were formed. Additionally, a sample not flushed

with argon gas or sealed prior to placing the sample in the oven was degraded at the 300ºC

temperature along side two samples which were pyrolyzed at the same time utilizing the

usual protocol.

4.4.1. Analysis with a Higher Cut-Off Mass

A set of samples were prepared using the revised procedure, namely a 7:1:5 mixing

ratio of the matrix, AgTFA and PP pyrolyzates, with the PP samples being prepared at 30

mg/ml. This set was pyrolyzed at 125º, 150º, 175º and 300ºC, but only the two highest temperatures yielded useable data. This section will discuss the observations from these

experiments, see figures 4.28 and 4.29.

The first observation was an increased intensity of pyrolysis products due to the more

efficient removal of the matrix. It was also observed that most peak clusters appeared to

70 have complex patterns indicative of more than one product. The additional products are unknown as it was impossible to resolve the clusters with other techniques to better understand their composition.

The blocking of the matrix allowed the observation of monoisotopic peaks out to

2300 Da and unresolved isotopic clusters out to 3600 Da (175ºC), which is close to the Mn of the amphorous PP analyzed, see table B.9 for full mass table. In the spectrum of the sample pyrolyzed at 175ºC the C fragment was dominant. At 300ºC the incidence of the A, Band C fragments appears to be comparable, with A now being the most abundant in terms of total intensity. Thus, at 300ºC there is a shift from C to A fragments being most abundant. It is noteworthy, however, that above ~1800 Da structure C continues to dominate at 300ºC.

Similar trends have been seen by other methods.4

While blocking the matrix did allow for better peak identification farther out into the

mass range, it did not provide data at all temperatures to help the temperature to temperature

correlation. Additional work is needed to improve and temperature to

temperature correlation. The higher mass cut-off allowed the observation of nearly the entire mass range of the polymer of interest. This was significant as it has the potential for identifying the Mn of an unknown polymer by using a low temperature pyrolysis profile.

4.4.2. Oxygen Experiments

Based on the knowledge that the material evaluated was a commercially produced PP

and that commercial processes are not tightly controlled and can be readily introduced

to the polymer matrix somewhere in its production, it was decided to determine if oxygen

71 contamination was present in the polymer. To test this theory several samples were pyrolyzed at the higher temperatures, namely 275º and 300ºC. Additionally, one sample as mentioned previously was allowed to be degraded at the 300ºC setting for 30 minutes.

These samples were then prepared using the revised procedure (glass vials, higher sample concentration) with the following modification. Different salts were added to ascertain if oxygen was present. For each pyrolyzate three samples were made, one with NaTFA, one with AgTFA and one with LiTFA. The silverated sample was prepared to verify that the same results are observed as in the previous experiments. The sodium and ions were used to verify the presence of oxygen. Na+ and Li+ have significant binding affinities to oxygen containing and, thus, would selectively ionize such compounds if they were present in the pyrolyzates. (such as A, B or C) do not ionize with Na+ or Li+ upon MALDI. Sodiated or lithated ions can easily be distinguished from silverated ions based on the corresponding unique isotopic distributions. After these samples were analyzed using the same MALDI-TOF conditions, the following observations were made. Only the silverated samples resulted in observable signals. Neither the sodiated nor lithated samples were capable of producing spectra. Additionally, the degraded sample (in presence of O2) yielded the same results as the pyrolyzed samples with only the silverated pyrolyzates providing a spectrum and producing similar isotope clusters as the pyrolyzed samples. Since the silverated samples, including the degradated sample, produced typical spectra (as previously described) no example from these experiments will be added. This work conclusively showed that no oxygen containing material was present in the pyrolyzates.

72

100% C

C

A C

C

C

% 50% C 73 C C A C C C C C C C C C C C C C C C C CC C C C C C

0%

1200 1400 1600 1800 2000 2200 2400

m/z

Figure 4.28. MALDI-TOF mass spectrum of PP pyrolyzates formed at 175ºC, acquired using a high mass cut-off.

C

2400

C

C

2200

C

C

2000

C

A m/z tes formed at 300ºC, acquired using a high C 1800

A

A

A A 1600 A C B

A C B A C

B A C B 1400 A C B A C

B A C B

A C B A mass cut-off. mass cut-off. Figure 4.29. MALDI-TOF mass spectrum of PP pyrolyza

1200

0%

50% 100% %

%

74 4.5. Mechanism Review

The thermal decomposition mechanism for this polymer is straight forward due to the

numerous references available for free-radical degradation of polyolefins. One reference that

has been cited most frequently, is the study published by Lattimer.4 This paper provides a practical guideline for deriving the mechanism shown over the next several pages. The PP used for this study was an amphorous PP terminated on both ends with methyl groups, see figure 3.1. Although many isomers can be drawn for each of these pathways, only one representative will be shown here; all isomers are displayed in appendix A.

In scheme 4.1, the initial cleavage sites are denoted as bonds of type I and II.

Radicals 1* and 2* formed when I undergoes homlytic cleavage. These two radicals can then

undergo intermolecular H* abstraction to form the isomers 1*-H and 2*-H which contain

double bonds in the newly created chain ends and thus, are ionizable by Ag+ additions.

These two isomers were designated in the prior text as fragment A and, after MALDI; they

generate silverated ions at m/z 42n + 56 + 107. Alternatively, radicals 1* and 2* may

undergo backbiting rearrangements as shown for 1* in scheme 4.2. In this scheme, 1* reacts via a 1,5-rH*or a 1,4-rH* followed by β-scission. The 1,4-rH* results in an alternate path to

1*-H and the 1,5-rH* results in a new fragment, designated 3*-H. The 3*-H fragment was

designated by B in the prior text and, after MALDI, gives rise to ion series m/z 42n + 70 +

107. In scheme 4.3, radical 2* is shown to undergo the same types of backbiting

rearrangements as 1* in scheme 4.2. This results in another path to 2*-H (from the 1,4-rH*) and a new fragment designated 4*-H. The 4*-H fragment was referred to as fragment C in the

prior text and, after MALDI, gives ions appearing at m/z 42n + 84 + 107. Due to both ends

of the PP being terminated with a methyl, when the chain is cleaved at site II we obtain

75 similar products to those illustrated in schemes 4.1 – 4.3. The intermolecular H* rearrangements lead to the fragments 3*-H and 4*-H which were originally shown in schemes

4.2 and 4.3, respectively. When radical 3*, i.e. the primary radical arising from the cleavage

of bond II, undergoes 1,5-rH* and 1,4-rH* one obtains isomers of 2*-H and 1*-H, respectively. When radical 4* undergoes the intramolecular rearrangements one obtains

isomers of 4*-H from the 1,5-rH* and isomers of 2*-H from the 1,4-rH*. See appendix A for

the isomers of these fragments.

76

I II

CH3 CH3 CH3 CH3

H3C CH CH CH CH C C C C CH3 H2 H2 H2 H2 n n

I Initial cleavage

CH CH CH CH 3 3 3 3 + H3 C CH CH CH CH * C C H2C C CH3 H2 H2 * H2 n n 1* * 2

Intermolecular H• loss

Ag+ Ag+ CH3 CH3 CH3 H H2 CH C C H C CH or H C C C H C C 2 H2 H2 H2 H CH3 n n

* 1 -H (A) 2* - H (A)

Scheme 4.1. Initial cleavage of bond I followed by H* loss to form truncated PP chains with olefinic chain ends.

77

CH3 CH3

CH * H3C CH 1 * C C H2 H2 n

* 1,4-rH* 1,5-rH

Intramolecular (backbiting)

CH3 CH3 CH3 CH3 CH3 CH3 CH3

H3C CH CH CH2 H3C CH C CH CH2 C C C C C C C H2 n-1 H H2 H2 H2 H2 H2 n-2

β-scission β-scission

Ag+ H2 H Ag+ H C C H2 H2 C CH CH C C CH2 H2 n-1 H C CH C 3 n-2 CH3 CH3

CH CH 3 3 1*-H (A) 3*-H (B)

Scheme 4.2. Backbiting rearrangements in secondary radical 1* followed by β-scission.

78

CH3 CH3

* 2 CH CH H2C C CH3 H * 2 n

1,4-rH* 1,5-rH*

backbiting

* H2 H2 H2 H H2 H C C C CH H C C C C CH 3 * 3 3 3 CH C CH CH CH CH CH n-1 n-2 CH3 CH3 CH3 CH3 CH3 CH3 CH3

β-scission β-scission

Ag+ Ag+ H2 H H2 H2C C CH3 C C CH3 C CH HC CH CH n-1 n-2 CH3 CH3 CH3 CH3 CH3

* 2 -H (A) 4*-H (C)

Scheme 4.3. Backbiting rearrangements in primary radical 2* followed by β-scission.

79 4.6. Future Work

Several areas for improvement and modification were identified in this study.

First, the sample preparation steps necessary to obtain a solublized sample would need to be addressed to obtain a more consistent concentration. Additional pyrolysis methods may need to be evaluated to determine if another method would increase the correlation between replicates and temperatures. It may also be of value to experiment with the pyrolysis time as well as the time between finishing pyrolysis and preparing the samples for MALDI-TOF analysis. Experiments need to be conducted to obtain MS/MS profiles to better explain which degradation pathway is the preferred route to a given fragment. Additional replication is necessary to quantify the qualitative results described in this thesis. Experimentation to find the “best” pyrolysis temperature for sample identification needs to be conducted. A point of interest for potential future investigation was the effect of a possible threshold temperature for optimum fragmentation. The 225º, 250º and 300ºC temperatures had fairly consistent fragments for the 26-mer through the 40-mer; whereas the lower temperatures were sporadic in the fragments observed through the mass range. Evaluation of additional polypropylene samples, both known and unknown need to be conducted to validate the theory that this method can be utilized for polypropylene characterization. As future work is conducted, additional issues may come to light which will be addressed as appropriate.

4.7. Summary of all Temperatures.

In the course of analyzing the data generated from these experiments several overall observations could be made. First, as temperature increased from 125º through 300ºC the fragmentation increased; while this is generally seen in most pyrolysis-MS studies, it was not

80 evident when these experiments were started which temperature or set of temperatures would provide the best data. Ideally, this temperature would render a mass spectrum that also characterizes the mass of the base polymer. The ability to observe mass values approaching the Mn of the polymer of interest is an important component for utilizing this method for future characterization work. Another observation was that the sample preparation techniques utilized for polyolefin analysis must be done in the absence of polyolefin containing vessels to minimize contamination. While similar spectra were able to be produced in the absence of PP sample tubes, it can not be eliminated as a source of interference or complication in future work and thus should be avoided. The lower temperature provided the most consistent data for these experiments. This may allow for more rapid identification with less expensive equipment which would be necessary for achieving the higher pyrolysis temperatures.

The fragmentation information provided somewhat inconsistent results. While the A fragment was generally the most abundant, a few replicates showed C to be the most abundant and additionally due to the high noise it was not obvious if or when the most abundant product changes from one fragment type to another.

General correlation between replicate analyses was very low to nonexistent in this study which points to the need for improved technique to be able to quantify future results.

Due to the lack of correlation within a temperature it was not going to be possible with this data to achieve correlation from temperature to temperature as seen in the high mass experiments. However, all the experiments showed one fact, namely that this method was capable of identifying a commercial PP based on its pyrolysis products.

81 CHAPHTER V

CONCLUSION

The purpose of these experiments was to demonstrate the capability of mild

pyrolysis in conjunction with MALDI-TOF MS to characterize a commercial

polypropylene. The methods and procedures described showed that a saturated olefin

could indeed be characterized using this methodology.

An amorphous PP with a Mn ~3700 was utilized for this study which was pyrolyzed under mild conditions at 125º-300ºC. The pyrolyzates were then prepared for

MALDI-TOF MS analysis using appropriate conditions to achieve interpretable spectra.

The spectra yielded the following information. The combination of temperatures and

mass ranges probed allowed the observation of detectable fragments from ~709 Da

through 3000+ Da which was the approximate Mn of the polymer of interest.

The measured peaks could be classified into three different PP distributions,

appearing at m/z 42n + 107 (C) , 42n + 14 + 107 (A) and 42n + 28 + 107 (B).4 There was limited ability to identify dominant fragment clusters based on abundances for a given temperature; those at m/z 42n + 14 + 107 (A) appeared to dominate at most temperatures.

The 42n + 107 (C) oligomers; become dominant over a certain mass in certain replicates.

Due to the lack of statistical similarity, quantification of these conclusions was not

82 possible based on these experiments. However, the qualitative data showed the adherence to the free-radical degradation mechanism which is readily accepted as the dominant mechanism for this type of polymer.

A set of future options was laid out to attempt to correct the issues addressed.

These included improved sample preparation, possible modification to the pyrolysis procedures, MS/MS analysis, and other experimental modifications to produce data which can be quantitatively interpreted. While additional work will need to be conducted to refine this to a reproducible procedure, the qualitative observations made in this study show the promise of using such a technique for saturated polyolefin identification and characterization which has not previously been recorded using this type of MS analysis.

Additionally, this method demonstrated the sensitivity of MALDI-TOF MS to identify like material contamination and as a result reinforced the utilization of good lab practices.

82 BIBLIOGRAPHY

1Pasquini, N. ed.; Polypropylene Handbook, 2nd Ed. (Cincinnati: Hanser Gardner Publications, Inc., 2005) 475-488.

2Pasch H.; Schrepp W.; MALDI-TOF Mass Spectrometry of Synthetic Polymers, (New York: Springer, 2003).

3de Hoffmann E.; Stroobant V.; Mass Spectrometry Principles and Applications, 2nd Ed., (New York: Wiley, 2002).

4Lattimer R.P.; “Pyrolysis field ionization mass spectrometry of polyolefins,” Journal of Analytical and Applied Pyrolysis. 1995, 31, 203-225.

5Blazsó M.; “Review: Recent trends in analytical and applied pyrolysis of polymers,” Journal of Analytical and Applied Pyrolysis. 1997, 39, 1-25.

6Nielen, Michel W. F.; “MALDI Time-of-Flight Mass Spectrometry of Synthetic Polymers,” Mass Spectrometry Reviews. 1999, 18, 309-344.

7Murgasova R.; Hercules D. M.; “MALDI of synthetic polymers-an update,” International Journal of Mass Spectrometry. 2003, 226, 151-162.

8Montaudo G.; Lattimer R. P.; Mass Spectrometry of Polymers. (New York: CRC Press, 2002).

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10Irwin W. J.; Analytical Pyrolysis, A Comprehensive Guide. (New York: Marcel Dekker, Inc., 1982) 3-8, 171-229, 293-319.

11Wampler T. P.; Applied Pyrolysis Handbook. (New York: Marcel Dekker, Inc., 1995) 1-27, 80-95.

84 12Kruse T. M.; Wong H.; Broadbelt L. J.; “Mechanistic Modeling of Polymer Pyrolysis: Polypropylene,” . 2003, 36, 9594-9607.

13van der Ven S.; Polypropylene and other Polyolefins: Polymerization and Characterization. (New York: Elsevier Science, 1990) 134-208.

14Painter P. C.; Coleman M. M.; Fundamentals of an Introductory Text, 2nd Ed., (Lancaster: Technomic Publishing AG, 1997) 1-60.

15Reflex III, MALDI-TOF Mass Spectrometer User’s Guide, Manual version 1.1, (Bruker Analytical Systems, Inc.) 1.2-1.23.

16Yalcin T.; Wallace W. E.; Guttman C. M.; Li L.; “ Powder Substrate-Assisted Laser Desorption/Ionization Mass Spectrometry for Polyethylene Analysis,” . 2002, 74, 4750-4756.

17Ishikawa T.; Ohkawa T.; Suzuki M; Tsuchiya T.; Takeda K.; “Semiquantitative Analysis of the Thermal Degradation of Polypropylene,” Journal of Applied Polymer Science. 2003, 88, 1465-1472.

18Yuan-Qing X.; Patel S.; Bakhtiar R.; Franklin R. B.; Doss G. A.; “Identification of a New Source of Interference Leached from Polypropylene Tubes in Mass-Selective Analysis,” J Am Soc Mass Spectrom. 2005, 16, 417-421.

19Royo E.; Brintzinger H.; “Mass spectrometry of and polypropylene complexes. A new tool for polymer characterization,” Journal of . 2002, 663, 213-220.

20Chen R.; Yalcin T.; Wallace W. E.; Guttman C. M.; Li L.; “Laser Desorption Ionizayion and MALDI Time-of-Flight Mass Spectrometry for Low Polyethylene Analysis,” J Am Soc Mass Spectrom. 2001, 12, 1186-1192.

21Billmeyer, Jr. F. W.; Textbook of Polymer Science, 2nd Ed., (New York: Wiley- Interscience, 1971).

85

APPENDICES

86 APPENDIX A

ISOMERS OF FRAGMENTS

CH CH 3 3

H2 CH C H C H2C C H C H H 2 n n

CH CH 2 2

H2 CH C H C H3C C H C H H 2 2 n n

Figure A.1. PP isomers with mass 42n + 56 (A fragment); after MALDI, these oligomers give rise to the m/z 42n + 56 +107 ion series.

87

H H CH CH 2 2 3 2 C C CH 2 H C CH C 3 H C CH C n 3 C C CH 3 CH CH H H 3 3 2 2 n

H 2 H C C CH 3 H C CH C 3 n

CH CH 3 3

Figure A.2. PP isomers with mass 42n + 70 (B fragment); after MALDI, these oligomers give rise to m/z 42n + 70 + 107 ion series.

88

H H2 H2 H2 C C CH3 C C CH3 HC CH CH n HC CH CH n CH3 CH3 CH3 CH2 CH3 CH3

H H2 H2 H2 C C CH3 C C CH3 H2CCCH H2CCCH n n

CH3 CH3 CH3 CH3 CH2 CH3

Figure A.3. PP isomers with mass 42n + 84 (C fragment); after MALDI these oligomers give rise to m/z 42n + 84 + 107 ion series.

89 APPENDIX B

MASS TABLES

Table B.1. 150ºC replicate a mass table Mass (Da) End Group Mer Mass (Da) End Group Mer 780 C 16 2040 C 46 822 C 17 2082 C 47 864 C 18 2124 C 48 906 C 19 2166 C 49 948 C 20 2208 C 50 990 C 21 2250 C 51 1032 C 22 2293 C 52 1074 C 23 2335 C 53 1116 C 24 2378 C 54 1158 C 25 2420 C 55 1200 C 26 2462 C 56 1242 C 27 2504 C 57 1284 C 28 2546 C 58 1326 C 29 2588 C 59 1368 C 30 2630 C 60 1410 C 31 2673 C 61 1452 C 32 2714 C 62 1494 C 33 2756 C 63 1536 C 34 2799 C 64 1578 C 35 2842 C 65 1620 C 36 2883 C 66 1662 C 37 2925 C 67 1704 C 38 2967 C 68 1746 C 39 3008 C 69

90 Table B.1. 150ºC replicate a mass table (con’t). 1789 C 40 3051 C 70 1831 C 41 3091 C 71 1872 C 42 3134 C 72 1914 C 43 3178 C 73 1956 C 44 3221 C 74 1998 C 45 Note: Italicized and underlined indicates average masses used.

Table B.2. 150ºC replicates b, c and d mass correlation table with normalization data. Mass (Da) b intensity c intensity d intensity End Group Mer 710 0.395 A 16 724 0.102 B 17 738 -0.768 C 17 780 0.768 C 16 794 -0.471 0.057 3.592 A 16 808 -0.687 -0.014 1.895 B 17 822 -0.303 C 17 836 -0.944 A 17 947 0.369 C 20 1004 0.600 1.951 -0.799 A 21 1018 0.231 0.771 -0.837 B 22 1032 0.127 0.857 -0.860 C 22 1046 -0.134 0.141 -0.826 A 22 1060 -0.472 -0.262 -1.044 B 23 1228 -0.807 -0.377 B 27 1242 -0.819 -0.483 C 27 1256 -0.951 A 27 Note: Italicized masses indicate sodiated peaks.

91 Table B.3. 175ºC replicates b, c and d mass correlation table with normalization data. Mass (Da) b intensity c intensity d intensity End Group Mer 710 0.442 A 14 724 0.019 B 14 738 -0.649 C 14 780 -0.350 C 16 794 0.046 0.622 3.480 A 16 808 -0.236 0.150 1.706 B 16 822 -0.213 C 17 836 -0.853 A 17 905 2.062 C 18 946 0.906 C 19 1004 0.536 2.735 -0.801 A 21 1018 0.627 0.957 -0.816 B 21 1032 0.642 0.978 -0.763 C 21 1046 -0.175 0.070 -0.874 A 22 1060 -0.196 -0.116 -0.925 B 22 1073 -0.288 -0.377 C 22 1157 -0.400 C 24 1199 -0.536 C 25 1228 -0.511 -0.129 -1.069 B 26 1241 -0.504 -0.275 -1.053 C 26 1256 -0.663 -0.447 -1.088 A 27 1270 -1.091 B 27 1283 -0.581 C 27

Table B.4. 200ºC replicates b and c mass correlation Mass (Da) b intensity c intensity End Group Mer 710 1730 A 16 724 887 B 17 738 725 C 17 754 1179 A 15 794 3013 A 16 878 1083 A 18 892 1907 1229 B 19 906 2999 2285 C 19 921 4661 854 A 19

92 Table B.4. 200ºC replicates b and c mass correlation (con’t). 933 3770 493 B 20 946 3977 C 20 948 4987 C 20 960 3288 A 20 1004 8018 A 21 1018 4716 B 22 1032 4013 C 22 1046 2903 A 22 1060 2423 B 23 1075 2455 C 23 1103 535 B 24 1118 1369 C 24 1130 2315 509 A 24 1142 5143 479 B 25 1159 4742 C 25 1171 3969 A 25 1187 4407 B 26 1202 4924 C 26 1215 5511 A 26 1230 6337 B 27 1244 5499 C 27 1257 5291 A 27 1272 4398 B 28 1286 4211 C 28 1300 3992 A 28 1314 4252 B 29 1328 4178 C 29 1341 4101 670 A 29 1356 3764 B 30 1369 3650 256 C 30 1382 2979 A 30 1399 2998 B 31 1411 3070 C 31 1426 3688 A 31 1440 3449 B 32 1454 3453 C 32 1468 3317 A 32

93 Table B.4. 200ºC replicates b and c mass correlation (con’t). 1481 2629 B 33 1495 2713 C 33 1510 2661 A 33 1526 2776 B 34 1537 2875 C 34 1554 2765 A 34 1566 2578 B 35 1582 2606 C 35 1595 2622 A 35 1608 2355 B 36 1623 2504 C 36 1678 2404 A 37 1691 2197 B 38 1706 2026 C 38 1720 2107 A 38 1736 2058 B 39 1748 2123 C 39 1761 2042 A 39 1775 1944 B 40 1792 1866 C 40 1804 1813 A 40 1830 1748 C 41 1848 1664 A 41 1862 1722 B 42 1874 1756 C 42 1891 1777 A 42 1904 1732 B 43 1918 1707 C 43 1931 1612 A 43 1945 1575 B 44 1974 1687 A 44 1986 1692 B 45 2000 1568 C 45 Note: Italicized and underlined values indicate average mass values were used.

94 Table B.5. 225ºC replicates a and c mass correlation.

Mass a intensity b intensity End Group Mer 710 1723 A 14 724 1020 B 15 738 15172 1302 C 15 752 1133 A 15 766 5529 B 16 780 32641 C 16 794 14301 A 16 808 9666 B 17 822 22875 823 C 17 836 9045 945 A 17 850 6881 675 B 18 892 5050 B 19 906 10981 C 19 920 4914 A 19 934 3990 B 20 948 8262 1361 C 20 962 1944 A 20 990 7819 1718 C 21 1004 4894 1838 A 21 1018 3042 B 22 1032 7294 C 22 1046 1245 A 22 1060 2327 1186 B 23 1074 5788 C 23 1088 1228 A 23 1102 3035 1259 B 24 1116 5339 C 24 1130 2647 3809 A 24 1144 2483 1191 B 25 1158 4561 1276 C 25 1172 2141 1098 A 25 1200 3663 1136 C 26 1214 2454 A 26 1228 1897 1000 B 27 1242 3883 1002 C 27 1256 1877 875 A 27

95 Table B.5. 225ºC replicates a and c mass correlation. (con’t). 1270 1583 939 B 28 1284 3147 962 C 28 1298 1740 A 28 1312 1896 781 B 29 1326 2762 1027 C 29 1340 1457 491 A 29 1368 2389 C 30 1382 1384 A 30 1410 1961 909 C 31 1424 1348 847 A 31 1438 1056 B 32 1452 1764 C 32 1480 912 B 33 1495 1489 C 33 1509 980 A 33 1536 1485 C 34 1579 1347 C 35 1593 2537 A 35 1608 2230 B 36 1620 1154 C 36 1636 2630 A 36 1651 1986 B 37 1662 1128 C 37 1678 2302 A 37 1692 1920 B 38 1704 983 C 38 1721 2138 A 38 1734 1943 B 39 1747 1064 C 39 1761 1737 A 39 1776 1765 B 40 1788 834 C 40 1805 1768 A 40 1819 1557 B 41 1831 993 C 41 1847 1917 A 41 1860 1444 B 42

96 Table B.5. 225ºC replicates a and c mass correlation. (con’t). 1874 842 C 42 1889 1664 A 42 1901 1571 B 43 1916 695 C 43 1932 1415 A 43 1944 1482 B 44 1958 772 C 44 1975 1643 A 44 1989 1198 B 45 2001 1969 C 45 2017 1231 A 45 2029 1289 B 46 2042 1656 C 46 2057 1440 A 46 2075 1072 B 47 2084 1853 C 47 2099 1298 A 47 2127 1999 C 48 2142 1231 A 48 2156 1210 B 49 2168 1670 C 49 2183 1237 A 49 2199 1290 B 50 2211 1753 C 50 2226 1175 A 50 2240 1075 B 51 2252 1344 C 51 2296 1630 C 52 2336 1285 C 53 2380 1346 C 54 2422 1245 C 55 2463 1177 C 56 2507 1317 C 57 2549 1218 C 58 2590 1187 C 59 2633 1033 C 60 2674 1022 C 61

97 Table B.5. 225ºC replicates a and c mass correlation. (con’t). 2716 1098 C 62 2759 1037 C 63 2801 991 C 64 2844 893 C 65 2885 891 C 66 2927 940 C 67 Note: Italicized and underlined values indicate average mass values were used.

Table B.6. 250ºC replicates a, b and c mass correlation. Mass (Da) a intensity b intensity c intensity End Group Mer 709 4132 2973 A 14 723 4493 2225 B 14 737 14203 2021 C 14 751 2025 A 15 765 60454 10158 B 15 779 29658 4169 C 15 793 22250 7983 A 16 807 11686 5132 B 16 821 21990 1540 C 16 835 14494 1546 A 17 849 7896 B 17 877 10510 7850 A 18 891 5608 1922 B 18 905 10549 C 18 919 6753 3794 A 19 933 4603 3424 1535 B 19 947 8087 4232 1163 C 19 961 5965 4360 1382 A 20 975 1040 B 20 989 7651 1123 C 20 1003 6785 8281 1598 A 21 1017 3346 4776 1265 B 21 1031 6955 4644 1228 C 22 1045 4091 2914 940 A 22 1059 2619 1987 774 B 22 1073 5094 2332 708 C 23 1087 3074 2408 805 A 23 1101 2414 B 23

98 Table B.6. 250ºC replicates a, b and c mass correlation. (con’t). 1115 4896 C 24 1129 3175 2394 A 24 1143 2742 2245 2233 B 24 1157 4095 2032 2203 C 25 1171 3044 1882 1964 A 25 1185 1786 1993 B 25 1199 3135 1605 2001 C 26 1213 2972 2040 1812 A 26 1227 1967 2100 2050 B 26 1241 3487 1701 2124 C 27 1255 2478 1639 1959 A 27 1269 1459 1833 B 27 1283 3248 1297 2131 C 28 1301 3167 1492 1667 A 28 1311 1419 1505 B 28 1325 2474 1298 1700 C 29 1339 2011 1411 2033 A 29 1353 1391 1262 1467 B 29 1367 2214 1433 1736 C 30 1381 1515 1148 A 30 1409 1696 1004 1455 C 31 1423 1637 1175 1468 A 31 1437 1163 1258 B 31 1451 1550 999 1433 C 32 1465 1197 2829 1476 A 32 1480 885 2662 1304 B 32 1494 1209 2462 1162 C 33 1508 1139 2737 1092 A 33 1524 2470 1164 B 33 1536 1266 2502 1112 C 34 1550 1040 2662 1220 A 34 1564 2383 1192 B 34 1578 1172 2212 1152 C 35 1593 1373 2055 A 35 1605 2170 B 35 1618 3586 2316 C 35 1633 2825 2043 A 36 1647 2202 2287 B 36 1661 2986 2053 C 36 1675 2316 1907 A 37 1689 1884 1845 B 37 1702 2616 1940 C 37

99 Table B.6. 250ºC replicates a, b and c mass correlation. (con’t). 1716 2035 A 38 1732 1850 B 38 1746 2848 C 38 1760 2229 A 39 1774 1747 B 39 1787 2537 C 40 1801 1930 A 40 1815 1495 B 40 1830 2529 C 41 1841 1966 A 41 1858 1624 B 41 1869 1570 C 42 1885 1734 A 42 1900 1400 B 42 1913 2038 C 43 1928 1804 A 43 1941 1374 B 43 1955 1719 C 44 1970 1636 A 44 1984 1166 B 44 1997 1745 C 45 2012 1609 A 45 2025 1200 B 45 2040 1657 C 46 2055 1600 A 46 2083 1802 C 47 2096 1393 A 47 2109 1278 B 47 2124 1624 C 48 2141 1068 A 48 2152 1063 B 48 2166 1648 C 49 2180 1256 A 49 2196 1008 B 49 2208 1331 C 50 2224 1107 A 50 2235 1088 B 50 2251 1438 C 51 2263 1293 A 51 2293 1357 C 52 2337 1010 C 53 Note: Italicized and underlined values indicate average mass values were used.

100 Table B.7. 275ºC replicates a, b and c mass correlation. Mass (Da) a intensity b intensity c intensity End Group Mer 709 1358 A 14 723 1412 B 14 737 11050 1067 C 15 751 26511 3271 716 A 15 765 15828 B 15 779 29760 C 15 793 20501 A 16 807 11645 B 16 821 23420 C 16 835 14258 A 17 849 7019 B 17 877 2261 A 18 891 6205 1059 B 18 905 5273 2393 C 19 919 7307 8380 1718 A 19 933 5895 894 B 19 947 8819 12285 C 19 961 15170 A 20 975 24056 B 20 989 59177 C 21 1003 6886 16585 A 21 1017 9320 B 21 1031 7435 10297 C 22 1045 10382 A 22 1059 7123 B 22 1073 6186 8101 C 23 1087 9197 A 23 1101 6863 919 B 23 1115 5666 6031 726 C 24 1129 3563 6985 1175 A 24 1143 5756 483 B 24 1157 4627 5758 513 C 25 1171 3156 5523 A 25 1185 3639 B 25 1199 4082 5105 C 26 1213 3459 5583 A 26 1227 2449 4870 B 26

101 Table B.7. 275ºC replicates a, b and c mass correlation. (con’t). 1241 3951 4567 C 27 1255 2843 4364 A 27 1269 1949 3379 B 27 1283 3741 3284 C 28 1297 2778 A 28 1325 3193 3747 526 C 29 1339 2432 3874 410 A 29 1353 2500 486 B 29 1367 2998 3376 400 C 30 1381 1936 2901 A 30 1395 1476 B 30 1409 2257 C 31 1423 2316 3058 A 31 1437 3475 B 31 1451 2288 2353 C 32 1465 1496 2370 A 32 1479 1360 1852 B 32 1493 1861 1759 C 33 1507 1404 A 33 1535 1689 5567 C 34 1549 1348 5044 A 34 1563 4484 329 B 34 1577 1590 4734 C 35 1591 1262 4356 A 35 1605 3714 B 35 1619 1352 C 36 1633 4264 4632 A 36 1647 3406 4534 B 36 1661 1351 4174 C 37 1675 1131 3967 A 37 1689 2851 3302 B 37 1703 1165 3361 C 38 1717 988 A 38 1731 972 B 38 1745 1373 3406 C 39 1759 3047 3404 A 39 1774 2393 2895 B 39

102 Table B.7. 275ºC replicates a, b and c mass correlation. (con’t). 1786 3367 2835 C 39 1801 2611 2782 A 40 1815 2265 B 40 1829 3238 C 40 1842 2708 3154 A 41 1858 2525 2630 B 41 1871 2937 2944 C 42 1885 2585 2734 A 42 1900 2237 B 42 1912 2886 2548 C 42 1928 2196 A 43 1942 2152 B 43 1956 2912 C 44 1970 2407 2774 A 44 1985 2007 B 44 1998 2702 2209 C 45 2011 2105 2289 A 45 2025 1764 B 45 2038 1943 C 45 2053 1967 A 46 2070 2166 B 46 2083 2379 2376 C 47 2096 1967 1989 A 47 2107 1523 1737 B 47 2124 2293 1948 C 48 2139 1557 1889 A 48 2151 1514 1819 B 48 2167 2225 2088 C 49 2181 1973 1944 A 49 2194 1638 1864 B 49 2207 2049 1727 C 50 2222 1635 1679 A 50 2237 1478 1586 B 50 2250 1902 C 51 2266 1584 A 51 2292 1854 1714 C 52 2306 1610 1618 A 52

103 Table B.7. 275ºC replicates a, b and c mass correlation. (con’t). 2317 1430 1542 B 52 2334 1812 1541 C 53 2347 1468 1477 A 53 2363 1426 1321 B 53 2377 1812 1497 C 54 2390 1424 1671 A 54 2408 1278 B 54 2419 1597 C 55 2433 1423 A 55 2445 1228 B 55 2459 1470 C 56 2474 1398 A 56 2491 1330 B 56 2502 1474 C 57 2518 1321 A 57 2532 1267 B 57 2543 1463 C 58 2559 1288 A 58 2572 1183 B 59 2588 1475 C 59 2599 1237 A 59 2628 1316 C 60 2673 1264 C 61 2713 1484 C 62 2756 1351 C 63 2797 1195 C 64 2840 1208 C 65 Note: Italicized and underlined values indicate average mass values were used.

Table B.8. 300ºC replicates a, b and d mass correlation. Mass (Da) a intensity b intensity d intensity End Group Mer 709 2815 A 14 723 1843 B 14 737 1715 C 15 751 2237 A 15

104 Table B.8. 300ºC replicates a, b and d mass correlation. (con’t). 765 1583 B 15 779 1356 C 16 793 1031 3332 2086 A 16 807 970 2886 1214 B 16 821 1559 C 17 835 1697 A 17 849 1089 B 17 877 6019 2810 3088 C 18 904 4047 4939 1129 C 19 919 7073 1287 A 19 933 6146 1354 B 19 947 7100 932 C 20 961 6745 693 A 20 989 873 C 21 1003 2717 8486 989 A 21 1017 1909 6628 716 B 21 1031 2058 5696 692 C 22 1045 1587 5513 706 A 22 1059 1106 4178 667 B 22 1073 636 3838 571 C 23 1087 4100 691 A 23 1115 3626 C 24 1128 3158 2069 A 24 1142 2837 1417 B 24 1156 2685 1319 C 25 1170 2326 1392 A 25 1184 2452 1116 B 25 1199 1729 1137 C 26 1213 706 2441 1362 A 26 1227 982 1991 1322 B 26 1241 876 1821 1033 C 27 1256 622 2141 1180 A 27 1268 564 1369 981 B 27 1284 472 1459 984 C 28 1299 1383 1019 A 28 1311 1500 957 B 28 1325 1522 1350 891 C 29

105 Table B.8. 300ºC replicates a, b and d mass correlation. (con’t). 1340 1400 1413 987 A 29 1353 882 B 29 1366 1389 1732 827 C 30 1381 1243 1087 920 A 30 1395 842 B 30 1411 1116 945 C 31 1422 1021 894 A 31 1437 1235 994 B 31 1454 1403 C 32 1464 854 A 32 1482 1035 B 32 1495 1127 2177 C 33 1509 900 2444 A 33 1537 1187 2226 C 34 1549 2252 A 34 1564 2110 B 34 1578 956 2172 C 35 1593 2133 A 35 1606 1896 B 35 1620 989 1968 C 36 1633 1901 A 36 1647 1930 B 36 1662 975 2038 C 37 1676 984 1846 A 37 1686 1744 B 37 1703 1717 C 38 1718 1700 A 38 1736 1508 B 38 1748 835 C 39 1759 1799 A 39 1774 1584 B 39 1787 1657 C 40 1804 1507 A 40 1829 1465 C 41 1843 1596 A 41 Note: Italicized and underlined values indicate average mass values were used.

106 Table B.9. High mass cut-off mass correlation. Mass End (Da) 175C 200C 225C 250C 300C Group Mer 1213 14938 11910 5780 7443 A 26 1227 12676 14312 5777 10362 B 26 1241 8421 12081 6375 12468 C 27 1255 9838 27822 18272 13384 12931 A 27 1269 14239 13748 6080 9842 B 27 1283 9822 17135 13115 13700 8767 C 28 1297 8630 23363 16545 8090 12026 A 28 1311 10889 16269 6128 B 28 1325 8626 10832 7985 C 29 1339 10582 8978 A 29 1353 7396 7199 B 29 1367 6968 8271 6040 7069 C 30 1381 6852 3434 7407 A 30 1395 6057 6471 5573 B 30 1409 4818 6388 4444 5720 C 31 1423 9989 3106 6874 A 31 1437 6922 4882 B 31 1451 4489 4427 7569 3650 5018 C 31 1465 6178 2610 5516 A 32 1479 2527 6757 5615 4171 4408 B 32 1493 3377 3489 5629 2617 4428 C 33 1508 4874 14598 4965 A 33 1521 5738 5174 3403 4182 B 33 1536 3612 3006 6100 14438 4120 C 34 1550 5215 12954 4596 A 34 1565 4055 5244 3511 B 34 1578 2563 4587 11724 3402 C 35 1592 3358 A 35 1605 3278 4544 12282 3032 B 35 1620 2197 4257 3358 C 36 1633 10786 3226 A 36 1648 4292 2821 B 36 1662 2257 4276 2579 C 37 1675 3639 9240 2911 A 37 1689 3839 8234 2230 B 37 1704 1924 3078 2326 C 38

107 Table B.9. High mass cut-off mass correlation. (con’t). 1718 2935 7636 2475 A 38 1735 17227 11926 B 38 1746 1623 19373 7725 11622 C 39 1761 18741 12534 A 39 1776 17911 10534 B 39 1790 1363 6110 16833 6998 10877 C 40 1804 16064 6205 10796 A 40 1817 13133 9618 B 40 1831 1456 6087 17121 7058 12445 C 41 1846 16242 5874 10036 A 41 1860 15628 5319 9328 B 41 1874 1214 5309 16708 5692 9307 C 42 1890 5161 14789 5839 9593 A 42 1902 14348 5840 8607 B 42 1915 1046 13684 4941 8018 C 43 1931 12382 4860 9216 A 43 1945 4781 12227 5203 7899 B 43 1959 956 4176 12601 4898 8076 C 44 1974 12897 5303 8363 A 44 1990 974 4442 12117 7150 B 44 2002 12476 6774 C 45 2014 11636 7121 A 45 2029 3563 9797 6741 B 45 2040 841 3406 10967 10489 C 46 2056 10694 4279 6993 A 46 2071 10488 6295 B 46 2084 805 11097 6478 C 47 2100 10591 6299 A 47 2113 9743 5919 B 47 2126 942 9966 4354 5969 C 48 2143 11057 9040 A 48 2155 9081 5469 B 48 2168 588 9543 5499 C 49 2183 9663 5993 A 49 2198 9699 4013 5328 B 49 2210 606 10276 5698 C 50 2224 8943 5395 A 50

108 Table B.9. High mass cut-off mass correlation. (con’t). 2240 7942 4784 B 50 2250 481 8122 7769 C 51 2268 8535 3150 5091 A 51 2282 7940 4737 B 51 2295 547 8503 4418 C 52 2308 8551 5226 A 52 2325 7802 B 52 2337 630 7983 C 53 2351 8575 3175 7107 A 53 2369 6488 B 53 2379 2956 7133 C 54 2391 6980 A 54 2409 6931 B 54 2422 3829 7210 3472 C 55 2436 7093 A 55 2456 5702 C 55 2464 2693 C 56 2496 2879 C 56 2506 2736 C 57 2548 2402 C 58 2560 5312 A 58 2571 2536 B 58 2632 2547 C 60 2644 2658 A 60 2664 3897 C 60 2676 1799 C 61 2717 2446 2417 C 62 2757 1897 C 63 2769 3767 A 63 2793 1713 2233 C 63 2842 1737 C 65 2969 1656 C 68 2977 2679 A 68 3011 1610 1714 C 69 3080 2453 B 70 3093 1698 C 71 3164 1768 B 72

109 Table B.9. High mass cut-off mass correlation. (con’t). 3179 1371 C 73 3238 1581 B 74 3387 1539 C 78 3684 1299 C 85 Note: Italicized and underlined values indicate average masses mere used.

110 APPENDIX C

ANOVA RESULTS

Table C.1. ANOVA results for 150ºC replicates b, c and d. SUMMARY Groups Count Sum Average Variance d intensity 7 16701 2386 8260390 b intensity 7 13681 1954 520763 c intensity 7 20430 2919 1424713

ANOVA Source of Variation SS df MS F P-value F crit Between Groups 3265469 2 1632734 0.480 0.627 3.555 Within Groups 61235192 18 3401955

Total 64500661 20

Table C.2. ANOVA results for 175ºC replicates b, c and d. SUMMARY Groups Count Sum Average Variance b intensity 10 22105 2211 864799 c intensity 10 31569 3157 3214025 d intensity 10 18744 1874 8622121

ANOVA Source of Variation SS df MS F P-value F crit Between Groups 8844808 2 4422404 1.045 0.366 3.354 Within Groups 114308504 27 4233648

Total 123153312 29

111 Table C.3. ANOVA results for 250ºC replicates a, b and c. SUMMARY Groups Count Sum Average Variance a intensity 10 50619 5062 3393090 b intensity 10 39358 3936 3374012 c intensity 10 11398 1140 102340

ANOVA Source of Variation SS df MS F P-value F crit Between Groups 81561952 2 40780976 17.810 1.169E-05 3.354 Within Groups 61824972 27 2289814

Total 1.43E+08 29

Table C.4. ANOVA results for 275ºC replicates a, b and c. SUMMARY Groups Count Sum Average Variance a intensity 120 426144 3551 22566719 b intensity 84 423616 5043 49132640 c intensity 19 18845 992 372585

ANOVA P- Source of Variation SS df MS F value F crit Between Groups 285035121 2 142517560 4.631 0.011 3.037 Within Groups 6770155160 220 30773433

Total 7055190280 222

112 Table C.5. ANOVA results for 300ºC replicates a, b and d. SUMMARY Groups Count Sum Average Variance a intensity 34 47481 1397 1108796 b intensity 58 161326 2781 3215596 d intensity 47 58058 1235 288501

ANOVA Source of Variation SS df MS F P-value F crit 6.62E- Between Groups 74398391 2 37199195 21.699 09 3.063 Within Groups 2.33E+08 136 1714340

Total 3.08E+08 138

113