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Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry “MALDI-TOF MS” Has Not Been Widely Applied Due to the Saturated Nature of Polyolefins

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CHARACTERIZATION OF COMMERICAL POLYPROPYLENE BY MILD PYROLYSIS AND MASS 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 MASS SPECTROMETRY 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. Ionization Sources…………………………………………….. 5 2.3 Direct Pyrolysis Analysis of PP……………………………….. 5 2.4 Free Radical 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 Spectrometer………………….. 14 3.5.1 MALDI-TOF MS Instrument Conditions……………. 16 3.6 Oxygen 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. ISOMERS OF FRAGMENTS……………………. 87 APPENDIX B. MASS TABLES…………………………………... 90 APPENDIX C. ANOVA RESULTS………………………………. 111 vii LIST OF TABLES Table Page 3.1. Blank study mixture ratio……………………………………………………… 14 3.2. Monoisotopic and average masses 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 ions above m/z 700 cutoff mass) were recorded. An x indicates that this ion 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 monoisotopic mass) in the MALDI mass spectrum 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 mass spectrum 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 polymer derived from vinyl monomers and belongs to a class of economically important polymers 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
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