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Controlled/Living Radical Polymerization in Aqueous Media: Homogeneous and Heterogeneous Systems

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Prog. Polym. Sci. 26 =2001) 2083±2134

www.elsevier.com/locate/ppolysci

Controlled/living radical polymerization in aqueous media: homogeneous and heterogeneous systems

a

Jian Qiu , Bernadette Charleux , KrzysztofMatyjaszewski

  • b,
  • a

*

aDepartment of Chemistry, Center for Macromolecular Engineering, Carnegie Mellon University, 4400 Fifth Avenue,
Pittsburgh, PA 15213, USA

b

  • Â
  • Â
  • Â Â
  • Laboratoire de Chimie Macromoleculaire, Unite Mixte associee au CNRS, UMR 7610, Universite Pierre et Marie Curie,

Â
Tour 44, 1er etage, 4, Place Jussieu, 75252 Paris cedex 05, France

Received 27 July 2001; accepted 30 August 2001

Abstract

Controlled/living radical polymerizations carried out in the presence ofwater have been examined. These aqueous systems include both the homogeneous solutions and the various heterogeneous media, namely dispersion, suspension, emulsion and miniemulsion. Among them, the most common methods allowing control ofthe radical polymerization, such as nitroxide-mediated polymerization, atom transfer radical polymerization and reversible transfer, are presented in detail. q 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Aqueous solution; Suspension; Emulsion; Miniemulsion; Nitroxide; Atom transfer radical polymerization; Reversible transfer; Reversible addition-fragmentation transfer

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2084 2. General aspects ofconventional radical polymerization in aqueous media . . . . . . . . . . . . . . . . . . . . .2089
2.1. Homogeneous polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2089 2.2. Heterogeneous polymerizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2089
2.2.1. Suspension polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2090 2.2.2. Emulsion polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2091 2.2.3. Miniemulsion polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2094
3. Controlled/living free-radical polymerization methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2096
3.1. General features and experimental criteria for controlled/living polymerization . . . . . . . . . . . . .2096
3.1.1. Feature 1: internal ®rst-order kinetics with respect to monomer . . . . . . . . . . . . . . . . . . .2096 3.1.2. Feature 2: linear growth ofdegree ofpolymerization =DP n) with conversion . . . . . . . . .2096 3.1.3. Feature 3: narrow molar mass distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2097

* Corresponding author. Tel./fax: 133-1-44-27-70-89. E-mail addresses: [email protected] =B. Charleux), [email protected] =K. Matyjaszewski).

0079-6700/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII: S0079-6700=01)00033-8
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3.1.4. Feature 4: long-lived polymer chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2097
3.2. Stable free radical polymerization =SFRP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2098 3.3. Atom transfer radical polymerization =ATRP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2099 3.4. Reversible/degenerative transfer reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2100
4. Controlled/living radical polymerization in aqueous solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2101 5. Controlled/living radical polymerization in aqueous dispersed systems . . . . . . . . . . . . . . . . . . . . . . . .2104
5.1. Nitroxide mediated polymerization =NMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2105
5.1.1. Precipitation and dispersion polymerizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2105 5.1.2. Suspension polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2105 5.1.3. Emulsion polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2108 5.1.4. Miniemulsion polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2110
5.2. Atom transfer radical polymerization =ATRP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2112
5.2.1. Direct ATRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2113 5.2.2. Reverse ATRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2118
5.3. Reversible transfer radical polymerization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2119
5.3.1. Degenerative iodine transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2119 5.3.2. Reversible addition-fragmentation transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2120
5.4. Peculiarities ofkinetics in controlled/living emulsion and miniemulsion polymerizations . . . . . .2126
5.4.1. Nucleation step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2126 5.4.2. Kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2127
6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2129 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2130 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2130

1. Introduction

Since Staudinger [1] proposed the concept ofa chain polymerization and the basic structure ofa polymer molecule eight decades ago, polymer science and technology has experienced an immense development that has revolutionized the look ofthe world and the lief ofhuman beings. Numerous polymeric materials have been created thanks to continuous progress in understanding the fundamentals ofpolymerization. One ofthe greatest contributions to this ®eld from synthetic polymer chemists is the development ofliving polymerization methodology, which allows the preparation ofmacromolecules with the maximum degree ofstructural and compositional homogeneity. As a consequence, well-de®ned polymers with precise molar masses, compositions, topologies and functionalities can be tailor-made. This is a signi®cant step toward the ultimate goal ofpolymer synthesis, when the design ofnovel materials is only limited by the imagination ofhuman beings.
The terms of`living polymerization' and `living polymers' were introduced by Szwarc [2] in 1956, although prior to his classical work, Ziegler [3] and Flory [4] also described similar concepts. By de®nition, a living polymerization is a chain polymerization that proceeds without the occurrence of irreversible chain breaking processes, i.e. chain transfer and termination. For nearly 30 years after Szwarc reported his insightful work, living polymerization of vinyl monomers had been restricted to anionic polymerization systems. But in 1960s and 1970s, several cationic ring-opening polymerizations ofheterocyclic monomers were found to proceed with most undesirable side reactions virtually absent [5±7]. It was discovered that ifa dynamic equilibrium between an active and dormant species was formed, it allowed for ®ne tuning of the polymerization of tetrahydrofuran [8,9]. This concept of dynamic equilibrium was eventually extended to vinyl monomers in early 1980s, triggering the

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Nomenclature

ꢀn~†

[I] average number ofradicals per particle initiator concentration
[I]0 [M] initial initiator concentration monomer concentration
[M]0 initial monomer concentration AA acrylic acid ACPA see V-501 AEROSOL-MA80 sodium dihexyl sulfosuccinate AIBN azobisisobutyronitrile

  • AN
  • acrylonitrile

ATRP atom transfer radical polymerization BPMOA N,N-bis=2-pyridylmethyl)octylamine BPMODA N,N-bis=2-pyridylmethyl)octadecylamine BPO benzoyl peroxide Bpy Brij98 C12H25±=OCH2CH2)20±OH CD cyclodextrine CLP controlled/living polymerization cmc critical micelle concentration
2,20-bipyridine
CRP controlled/living radical polymerization CSA camphorsulfonic acid CTAB cetyl trimethyl ammonium bromide dAbpy 4,40-dialkyl-2,20-bipyridine, alkyl: mixture ofpentyl and 5-nonyl DCP dicumyl peroxide dHDbpy 4,40-di=9-heptadecyl)-2,20-bipyridine DMAEMA 2-=dimethylamino)ethyl methacrylate dNbpy 4,4-di=5-nonyl)-2,20-bipyridine DOWFAX8390 dihexadecyl disulfonated diphenyloxide disodium salt =Dow Chemical) DPn DPw DRI number average degree ofpolymerization weight average degree ofpolymerization differential refract0ive index detection dTbpy 4,40-di-t-butyl-2.2 -bipyridine EBiB ethyl 2-bromoisobutyrate Forafac C8F17CH2CH2COO2K1 =Ato®na) HEA 2-hydroxyethyl acrylate HEMA 2-hydroxyethyl methacrylate HLB hydrophilic-lipophilic balance HV25 nonionic poly=ethylene oxide) ꢀDPn ˆ 25† nonyl phenol surfactant =Witco) Ip ˆ DPw=DPn ˆ Mw=Mn polydispersity index

K

ka

activation/deactivation equilibrium constant =dimension depends on the system) rate constant ofactivation =dimension depends on the system)

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kd kp

rate constant ofdeactivation =l mol 21 s21) rate constant ofpropagation =l mol 21 s21)
Kraton copolymer ofethylene and butylene rate constant ofirreversible termination =l mol 21 s21) rate constant oftransfer =l mol 21 s21)

kt ktr

MALDI-TOF MS matrix-assisted laser desorption/ionisation Ð time-of-¯ight mass spectrometry Me6TREN tris[2-=dimethylamino)ethyl]amine MEMA 2-=N-morpholino)ethyl methacrylate MMA methyl methacrylate MMD molar mass distribution

Mn Mw NA

number average molar mass =g mol21) weight average molar mass =g mol21) Avogadro's number
NaMA sodium methacrylate NaSS sodium styrenesulfonate NaVBA sodium vinylbenzoate n-BA n-butyl acrylate n-BMA n-butyl methacrylate NMP nitroxide-mediated radical polymerization NMR nuclear magnetic resonance OEGMA oligo=ethylene glycol) methacrylate OP-10 polyoxyethylene nonyl phenyl ether P=NaSS) poly=sodium styrenesulfonate) P=n-BA) poly=n-butyl acrylate) P=n-BMA) poly=n-butyl methacrylate) PMDETA N,N,N0,N00,N00-pentamethyldiethylenetriamine PMMA poly=methyl methacrylate) PRE persistent radical effect PS polystyrene PVA poly=vinyl alcohol) PVP poly=N-vinylpyrrolidone) RAFT reversible addition-fragmentation transfer

Rp

Srate ofpropagation =mol l 21 s21) styrene
SDBS sodium dodecylbenzene sulfonate SDS sodium dodecyl sulfate SEC size exclusion chromatography SFRP stable free-radical polymerization

  • SG1
  • N-tert-butyl-N-=1-diethylphosphono-2,2-dimethylpropyl) nitroxide

TEMPO 2,2,6,6-tetramethyl piperidinyl-1-oxy tNtpy 4,40,400-tris=5-nonyl)-2,20:600,2-terpyridine Tween 80 sorbitane monooleate poly=ethylene glycol)

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  • UV
  • ultra-violet detection

V-40 1,100-azobis-=1-cyclohexane carbonitrile) V-50 2,20-azobis=2-methylpropionamidine) dihydrochloride V-501 4,40-azobis=4-cyanovaleric acid) =also called ACPA: 4,40-azobis=4-cyanopentanoic acid)) VA-0442,20-azobis[2-=2-dimidazolin-2-yl) propane] dihydrochloride VA-0862,2 -azobis[2-methyl-N-=2-hydroxyethyl) propionamide]

x

monomer conversion breakthrough discovery ofcationic vinyl polymerizations that proceeded in a controlled fashion under certain restrictive conditions [10±12]. Since then, extensive investigations ofvarious CLP mechanisms has been conducted [13,14]. The late 1980s and the entire 1990s witnessed a rapid expansion ofthe scope ofCLP. To date, the major classes ofchain polymerization, i.e. anionic [15±17], cationic [18,19], ring-opening metathesis [20,21], coordination [22] and radical polymerization [23,24], can become living or controlled under appropriate conditions. However, most ofthese polymerization techniques are not exempt from chain transfer or termination reactions. To differentiate these imperfect polymerizations from the ideal living polymerization, terms such as controlled, `living', pseudo-living, quasiliving and many others have been used in literature, which initiated an on going debate over nomenclature [25,26]. Until a uniform terminology is accepted, we will use the term `controlled/living polymerization' to describe all the polymerization processes from which polymers with predetermined molar masses, low polydispersities and high chain-end functionalities can be obtained. The signi®cance ofcontrolled/living polymerization as a synthetic tool is widely recognized. With polymers having uniform and predictable chain length readily available, it provides the best opportunity to control the bulk properties by variations at a molecular level. Furthermore, a variety ofnovel polymer materials with predetermined composition, topology and functionality, as illustrated in Table 1, can be created.
Among the numerous polymerization techniques, free-radical polymerization is a widely used process from the viewpoint of industrial production and applications [27]. This technique is relatively easy to perform since it does not require stringent puri®cation of the reagents, except the elimination of the dissolved oxygen. It generally leads to high molar mass polymers under relatively mild conditions. Polymerization temperatures can be usually set between room temperature and about 2008C. Many different processes can be applied such as bulk, solution, suspension or emulsion polymerizations. Moreover, a wide range ofufnctional monomers can be polymerized by a radical mechanism and copolymerizations have provided a great variety ofrandom copolymers with many structures and properties. The main limitations ofradical polymerization are the lack ofcontrol over the molar mass, the molar mass distribution, the end-functionalities and the macromolecular architecture. This is caused by the unavoidable fast radical±radical termination reactions. Mainly for that reason, the recent emergence ofmany so-called `living' or controlled radical polymerization =CRP) processes has opened a new area in this old polymerization method that had witnessed relatively small progress in the previous years.
Until now, CRP has been predominantly studied in homogeneous organic systems, i.e. bulk or solution polymerizations. With the rapid development ofunderstanding ofthose controlled systems, one ofthe biggest present concerns is: can these methods be extended to the aqueous media? Indeed, the polymerizations carried out in aqueous media are receiving more and more attention and, in contrast to

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Table 1 Polymers available by controlled/living polymerization techniques

the numerous controlled polymerization methods employed in organic media, aqueous polymerization is mainly focused on radical polymerization. Among the most important factors contributing to this trend are increased environmental concern and a sharp growth ofpharmaceutical and medical applications for hydrophilic polymers. Another important reason is that in industry radical polymerization is widely performed in aqueous dispersed systems, and particularly, in emulsion polymerization. This technique offers many invaluable practical advantages over homogeneous polymerizations, such as the absence of volatile organic compounds, better control ofheat transfer, and the possibility to reach high molar mass polymers with high conversion and a faster rate of polymerization than in bulk or solution systems. The

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®nal water suspension ofstable polymer particles =also called a latex) is easy to handle owing to a generally low viscosity, even at high solid content, and can be used directly for coating applications or as a dried polymer after removal of water.
Thus, it is obvious that a substantial progress in controlled free-radical polymerization would be achieved ifthis technique can be applied to either homogeneous or heterogeneous aqueous systems. The ®rst, and main goal is to control the characteristics ofthe polymer in terms ofmolar mass, molar mass distribution, architecture, and function. The rapid and very recent development of this domain will be illustrated in this review article. Polymerizations in aqueous solution will be considered ®rst, including the scope and limitations ofthe existing CRP systems. Then, the attention ofthe article will be focused on the application ofCRP in aqueous dispersed media using the suspension, dispersion, emulsion and miniemulsion polymerization processes. The kinetics ofpolymerization and control over the polymer characteristics will be examined for each CRP technique used and a comparison with homogeneous polymerization will be made. The repercussions ofCRP chemistry on the very mechanism ofthe heterogeneous polymerization systems will also be addressed with special attention.

2. General aspects of conventional radical polymerization in aqueous media

2.1. Homogeneous polymerization

One essential requirement for aqueous solution polymerization is that the monomer and the formed polymer should be suf®ciently water-soluble. Some typical water-soluble monomers are listed in Table 2.
Various radical initiation techniques, including thermal, redox, photochemical, electrochemical and radiolysis, have been employed for aqueous solution polymerizations [28]. Basically, the polymerization follows the same principles as those in the organic systems. There are, however, a few unique features for aqueous solution polymerization. In particular, it is often observed that monomers with ionizable pendant groups polymerize much faster in aqueous solutions than in bulk or in the presence of organic solvents. The overall rate ofpolymerization for such monomers increases by 1.5±2 orders ofmagnitude in aqueous solution. This kinetic variance is caused by a remarkably enhanced kp/kt ratio, which is generally attributed to a number offactors: =i) solvation ofthe monomer molecules, particularly via hydrogen bond formation with water, alters the electron density in the double bond of the monomer and hence its reactivity [29]; =ii) increased ionic dissociation ofthe pendant group produces greater electrostatic repulsion between the two growing radicals [30]; =iii) the existence ofpolymer±water interactions that produce a strongly bound hydration shell also helps to protect the propagating radical center from termination [31]. Therefore, changes of pH and ionic strength exert a pronounced in¯uence on the polymerization ofthese basic and acidic monomers. One ofthe consequences is that in copolymerization the reactivity ratios oftwo monomers, when one or both are ionizable monomers, vary with the degree of ionization. In contrast, monomers containing neutral hydroxy groups are less sensitive to pH and ionic strength variations. Such a stability ofthe water-structuring center makes the hydrogels derived from these monomers, such as 2-hydroxyalkyl =meth)acrylates, very attractive for biomedical applications.

2.2. Heterogeneous polymerizations

Although aqueous solution polymerizations are ofconsiderable interest, the number ofwater-soluble

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Table 2 Typical water-soluble monomers

  • Monomers with acidic functions
  • Monomers with basic functions

Acrylic acid Methacrylic acid Itaconic acid
Acrylamide Methacrylamide N-hydroxymethylacrylamide N,N-dimethylacrylamide N-isopropylacrylamide N-acetamidoacrylamide 2-Aminoethyl methacrylate N,N-dimethylaminoethyl methacrylate
Allenesulfonic acid Ethylenesulfonic acid Styrenesulfonic acid 2-Sulfoethyl methacrylate

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    Batch Emulsion Polymerization of Vinyl Chloride: Application of Experimental Design to Investigate the Effects of Operating Variables on Particle Size and Particle Size Distribution Mahdi Pourmehr, Amir H. Navarchian Department of Chemical Engineering, University of Isfahan, Isfahan, Iran Received 4 May 2008; accepted 7 July 2008 DOI 10.1002/app.29079 Published online 3 October 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: In this article, the influences of operating effects in the range of levels investigated in this study. variables on the particle size (PS) and particle size distribu- Except initiator concentration, all factors have important tion (PSD) of emulsion poly(vinyl chloride) in batch reactor influence on the PSD (significance sequence: S > R > T > were investigated using Taguchi experimental design [E]). It is implied from the greater influence of agitation approach. The variables were temperature (T), water to speed relative to temperature on PSD that the shear coagula- monomer weight ratio (R), concentrations of initiator ([I]) tion predominates the Brownian coagulation in this system. and emulsifier ([E]), and agitation speed (S). Scanning elec- The relative optimum condition for a typical paste applica- tron microscope was used together with image analysis soft- tion was also determined using overall evaluation criteria. ware to determine the PS and PSD. Statistical analysis of VC 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 338–347, 2009 results revealed that the PS of emulsion poly(vinyl chloride)
  • Synthesis and Characterization of Solution and Melt Processible Poly(Acrylonitrile-Co-Methyl Acrylate) Statistical Copolymers

    Synthesis and Characterization of Solution and Melt Processible Poly(Acrylonitrile-Co-Methyl Acrylate) Statistical Copolymers

    SYNTHESIS AND CHARACTERIZATION OF SOLUTION AND MELT PROCESSIBLE POLY(ACRYLONITRILE-CO-METHYL ACRYLATE) STATISTICAL COPOLYMERS Padmapriya Pisipati Dissertation submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Macromolecular Science and Engineering James E. McGrath, Chair Judy S. Riffle, Acting Chair Eugene G. Joseph Sue J. Mecham Donald G. Baird 02/20/2015 Blacksburg, VA Keywords: melt processability, polyacrylonitrile, carbon fibers, methyl acrylate, acrylic fibers, plasticizer, solution processing, high tensile modulus Copyright 2015, Padmapriya Pisipati SYNTHESIS AND CHARACTERIZATION OF SOLUTION AND MELT PROCESSIBLE POLY (ACRYLONITRILE-CO-METHYL ACRYLATE) STATISTICAL COPOLYMERS ABSTRACT Padmapriya Pisipati Polyacrylonitrile (PAN) and its copolymers are used in a wide variety of applications ranging from textiles to purification membranes, packaging material and carbon fiber precursors. High performance polyacrylonitrile copolymer fiber is the most dominant precursor for carbon fibers. Synthesis of very high molecular weight poly(acrylonitrile-co-methyl acrylate) copolymers with weight average molecular weights of at least 1.7 million g/mole were synthesized on a laboratory scale using low temperature, emulsion copolymerization in a closed pressure reactor. Single filaments were spun via hybrid dry-jet gel solution spinning. These very high molecular weight copolymers produced precursor fibers with tensile strengths averaging 954 MPa with an elastic modulus of 15.9 GPa (N = 296). The small filament diameters were approximately 5 µm. Results indicated that the low filament diameter that was achieved with a high draw ratio, combined with the hybrid dry-jet gel spinning process lead to an exponential enhancement of the tensile properties of these fibers.
  • Polymer Chemistry

    Polymer Chemistry

    CLOTHWORKERS LIBRARY UNIVERSITY OF LEEDS THERMAL AND OXIDATIVE DEGRADATION OF AN AROMATIC POLYAMIDE. by «. Shojan Nanoobhai Patel 2. Submitted in accordance with the requirement for the degree of Doctor of Philosophy under the supervision of Professor I.E. McIntyre and Dr. S.A. Sills. The candidate confirms that the work submitted is his own and that appropriate credit has been given where reference has been made to work of others. Department of Textile Industries, The University of Leeds, Leeds, LS2 9JT. December 1992. CLASS MARK T:; ~S 2tC\4 -1- ABSTRACT. The thermal oxidation of an aromatic polyamide fibre, namel\' poly(m-xylylene adipamide) has been investigated. The volatile and non-volatile products of oxidation identified using T.L.C., H.P.L.C. and G.C.-M.S. include homologous series of monocarboxylic acids, dicarboxylic acids, n-alkyl amines, diamines and aldehydes. Furthermore, several aromatics, ketones and amides were also identified. Mechanisms for their derivation have been proposed which are based on oxidation reactions already established in polymer chemistry. These include a mechanism of ~ scission by an alkoxy radical thought to be responsible for the creation of the homologous series. MXD,6 fibres were also spun incorporating 100, 200 and 400ppm of a cobalt catalyst and the effect of the metal ions on the oxygen uptake of the fibres was investigated. The results show a consistent increase in the rate of oxygen uptake as the concentration of the cobalt is increased. Furthermore, T.G.A. oxidative degradation studies, conducted at isothermal temperatures in the solid state, show decreases in the activation energies associated with fibre oxidation with increased cobalt concentrations, implying the cobalt is a catalyst for oxidation.
  • Polybenzimidazole Synthesis from Compounds with Sulfonate Ester Linkages

    Polybenzimidazole Synthesis from Compounds with Sulfonate Ester Linkages

    AN ABSTRACT OF THE THESIS OF Turgav Seckin for the degree of Master of Science in Chemistry presented on August 26, 1987 TITLE : Polybenzimidazole Synthesis Frog Comnounds with Sulfonate Ester Linkages Redacted for privacy Abstract approved : Dr. R.W. THIES This investigation of polybenzimidazole synthesis involvedthe two-stage low temperature solution polymerization of dialdehydes, One-step polycondensation of dialdehydes,two-stage melt polyconden- sation of diesters, and one-step solutionpolycondensation of diesters with 3,3'-diaminobenzidine. Dialdehyde or diester monomers were prepared which contained aromatic units whichwere hooked toget- her with sulfonate linkages. Polymerization of these monomers with 3,3'-diaminobenzidine resulted in moderate viscosities of0.4-0.8 dlg in DMSO at 19°C. The polybenzimidazoles obtained appear to be linear; most of them when tested immediatelyafter preparation, were largely soluble in certain acidicor dipolar approtic solvents. Films, obtained by dissolving the polymerin dipolar approtic solvents such as N,N-dimethylacetamideor N,N-dimethyl formamide, were flexible, clear, yellow to brown in color, and foldable depen- ding upon which monomers and which polymerization methodswere used. Polybenzimidazole Synthesis From Compounds with Sulfonate Ester Linkages by Turgay Seckin A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Completed August 26, 1987 Commencement June 1988 APPROVED Redacted for privacy Professor of Chemistry in Charge ofMajor Redacted for privacy Chairman of Department of Chemistry Redacted for privacy Dean of G ad ate School Date thesis is prepared August 17, 1987 Thesis typed by Turgay Seckin To my family for their never failing love andsupport NE MUTLU TURKUM DIYENE ACKNOWLEDGEMENT I would like to thank Prof.
  • Polymer Colloid Science

    Polymer Colloid Science

    Polymer Colloid Science Jung-Hyun Kim Ph. D. Nanosphere Process & Technology Lab. Department of Chemical Engineering, Yonsei University National Research Laboratory Project the financial support of the Korea Institute of S&T Evaluation and Planning (KISTEP) made in the program year of 1999 기능성 초미립자 공정연구실 Colloidal Aspects 기능성 초미립자 공정연구실 ♣ What is a polymer colloids ? . Small polymer particles suspended in a continuous media (usually water) . EXAMPLES - Latex paints - Natural plant fluids such as natural rubber latex - Water-based adhesives - Non-aqueous dispersions . COLLOIDS - The world of forgotten dimensions - Larger than molecules but too small to be seen in an optical microscope 기능성 초미립자 공정연구실 ♣ What does the term “stability/coagulation imply? . There is no change in the number of particles with time. A system is said to be colloidally unstable if collisions lead to the formation of aggregates; such a process is called coagulation or flocculation. ♣ Two ways to prevent particles from forming aggregates with one another during their colliding 1) Electrostatic stabilization by charged group on the particle surface - Origin of the charged group - initiator fragment (COOH, OSO3 , NH4, OH, etc) ionic surfactant (cationic or anionic) ionic co-monomer (AA, MAA, etc) 2) Steric stabilization by an adsorbed layer of some substance 3) Solvation stabilization 기능성 초미립자 공정연구실 기능성 초미립자 공정연구실 Stabilization Mechanism Electrostatic stabilization - Electrostatic stabilization Balancing the charge on the particle surface by the charges on small ions
  • 1 050929 Quiz 1 Introduction to Polymers 1) in Class We Discussed

    1 050929 Quiz 1 Introduction to Polymers 1) in Class We Discussed

    050929 Quiz 1 Introduction to Polymers 1) In class we discussed a hierarchical categorization of the terms: macromolecule, polymer and plastics, in that plastics are polymers and macromolecules and polymers are macromolecules; but all macromolecules are not polymers and all polymers are not plastics. a) Give an example of a macromolecule that is not a polymer. b) Give an example of a polymer that is not a plastic. c) Define polymer. d) Define plastic. e) Define macromolecule. 2) In class we observed a simulation of a small polymer chain of 40 flexible steps. The chain was observed to explore configurational space. a) Explain what the phrase "explore configurational space" means. b) Consider the two ends of the chain to be tethered with a separation distance of about 6 extended steps. If temperature were increased would the chain ends push apart or pull together the tether points? Explain why. c) If one chain end is fixed in Cartesian space at x = 0, what are the limits on the x-axis for the other chain end as it explores configurational space? d) What is the average value of the position on the x-axis? dγ 3) Polymer melts are processed at high rates of strain, , in an extruder, injection molder, or dt calander. a) Sketch a typical plot of polymer viscosity versus rate of strain on a log-log plot showing the power-law region and the Newtonian plateau at low rates of strain. b) Explain using this plot why polymers are processed at high rates of strain. c) Using your own words propose a molecular model that could explain shear thinning in polymers.
  • Solution Polymerization of Acrylic Acid Initiated by Redox Couple Na-PS/Na-MBS: Kinetic Model and Transition to Continuous Process

    Solution Polymerization of Acrylic Acid Initiated by Redox Couple Na-PS/Na-MBS: Kinetic Model and Transition to Continuous Process

    processes Article Solution Polymerization of Acrylic Acid Initiated by Redox Couple Na-PS/Na-MBS: Kinetic Model and Transition to Continuous Process Federico Florit , Paola Rodrigues Bassam , Alberto Cesana and Giuseppe Storti * Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Piazza Leonardo da Vinci, 32, 20133 Milano, Italy; federico.fl[email protected] (F.F.); [email protected] (P.R.B.); [email protected] (A.C.) * Correspondence: [email protected] Received: 28 May 2020; Accepted: 14 July 2020; Published: 16 July 2020 Abstract: This work aims at modeling in detail the polymerization of non-ionized acrylic acid in aqueous solution. The population balances required to evaluate the main average properties of molecular weight were solved by the method of moments. The polymerization process considered is initiated by a persulfate/metabisulfate redox couple and, in particular, the kinetic scheme considers the possible formation of mid-chain radicals and transfer reactions. The proposed model is validated using experimental data collected in a laboratory-scale discontinuous reactor. The developed kinetic model is then used to intensify the discontinuous process by shifting it to a continuous one based on a tubular reactor with intermediate feeds. One of the experimental runs is selected to show how the proposed model can be used to assess the transition from batch to continuous process and allow faster scale-up to industrial scale using a literature approach. Keywords: Poly(acrylic acid); free-radical polymerization; reaction model; process intensification; semi-batch to continuous 1. Introduction Poly(acrylic acid) (PAA) is a widely produced polymer with a growing, global annual production of 1.58 109 kg as of 2008 [1] and with applications in many industrial sectors.