Kinetic/Mechanistic Aspects of Radical Polymerization: Homogeneous and Heterogeneous Systems

Kinetic/mechanistic aspects of radical polymerization: Homogeneous and heterogeneous systems Yusuke Sugihara A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy 2014 March Centre of Advanced Macromolecular Design (CAMD) School of Chemical Engineering The University of New South Wales (UNSW) i Abstract The objective of this Thesis is to develop new contributions to the fundamental knowledge in the area of kinetics and mechanism of radical polymerization. Polymer science, the study of large molecules, is one of the most important subjects, which has led to the development and production of numerous of our commodities and household items such as plastics, fibres, elastic materials, paints, adhesives, and even electronic applications. The popularity and importance of polymer products has all through the ages been a sufficient impetus to improve various polymerization techniques, not only conventional bulk or solution homogeneous systems, but also various specific conditions such as heterogeneous systems, polymerization under microwave (MW) irradiation, as well as controlled/living radical polymerization. Regardless of the specific techniques, the understanding of kinetics and mechanism is of prime concern. Despite the far-reaching achievements thus far, the subject of radical polymerization is of course far from complete. Radical polymerization itself has been advancing and new techniques and new interests are continuously emerging. In this Thesis, the on-going argument of the possible influence of MW irradiation on the kinetics of radical polymerization was experimentally investigated precisely with the model monomer of styrene. The kinetics of emulsion polymerization of styrene, one of the most precisely studied heterogeneous systems was studied to investigate the practical limit of the particle size in which the standard kinetic concept of ’zero-one theory’ is valid. A theoretical study is described for the kinetics of nitroxide-mediated polymerization (NMP) of styrene in under heterogeneous conditions of miniemulsion polymerization, where the influence of the particle size ’compartmentalization’ and ingredient partition are successfully combined for the first time. Finally, the elemental reactions of chain transfer to solvent were investigated for the conventional radical polymerization and NMP for the combination of N-isopropylacrylamide (NIPAM) monomer and dimetylformamide (DMF) solvent, not only in order to evidence the chain transfer to solvent reaction for this particular case, but also to gain a general understanding on how such side reactions influence the polymerization process. ii Acknowledgement My thanks is first to my supervisor Professor Per Zetterlund. He provided the opportunity for this PhD study. Our acquaintance has been since when we were in Japan, and my story in Australia and Ireland was with his support. He is the only one person to be able to know my true history who I was and who I am and why, as such his words have been important supplement for me to find my personal legend. Since now is the time we see the answer of our effort in this period as what I becomes of. Hardships do lie ahead of my future, and my challenge is to return the favour as I reach make it to a truth. I thank Professor Tom Davis for the foundation of CAMD. CAMD is the group developed by him and in this place I met many nice and diligent scientists and friends. Thanks to Dr Michael Whittaker and Dr Istvan Jacenyik for the management of our group and for the favour to my repeated requests. I appreciate Dr. Fawaz Aldabbagh, Ireland my work were also under the supervision of him in NUIG. It was my first place I accumulated the common sense and requirement of Chemistry. It was the only time of less than 2 years, but perhaps my best life was there in Ireland. For the project, thanks to Dr Orla Gibbons and Dr Liz Donovan for their patient instruction, and thanks to Padraig O’Connor for his support and assistance in Ireland. My thanks go also A/Professor Brian Hawkett and Professor Sébastien Perrier for my works with KCPC. Here I add thanks to Dr Stuart Thickett, now he is in CAMD. For me it has a special meaning and since long ago they has been my direction and guide board as a novice of polymer chemist. It is my luck I can be acquainted with them and given their wisdom. I thank Dr Hank De Bruyn. My dilatometry work really is indebted to his patience. All the time I asked him help and all the time he fixed! I also thank Duc Nguyen and Binh Pham for their matured and experienced advice for emulsion polymerization, and also thank Eh Hau Pan for his kind help in the experiment there. Importantly, all my life in Sydney and Galway has been supported by really a lot of very nice and exciting friends. I must apologize that I cannot express my heartfelt gratitude to everyone individually, and also I cannot thanks enough. You gave me the real smile and happiness on my life, otherwise my life was dead and in the depth of despair. You really gave me lots of memories. I must challenge my life so that I can see you again in smile… I have other people I must express my gratitude about some works which is not yet published. I strive to make it for sure, and give back them as a certain establishment. Also this PhD thesis is not directly concerned, but at this time I am completing my PhD, I would like to express my sincere gratitude and respect for Professor Robert Gilbert and Professor Shigeru Yamago. My life as a novice of polymer chemist started by following their great jobs on emulsion polymerization and organotellurium-mediated living radical polymerization, and since then my effort has been to adore them in my heart up to now. All the time, it was/is difficult, I am still poor and deficient. However, I wish someday I return the great favour. Finally, I have the most important gratitude for my family. iii Table of Contents Chapter 1 Introduction 1 1.1 Overview 2 1.2 Aims and outline 5 1.3 References 6 Chapter 2 Literature Review 8 2.1 Radical Polymerization 9 2.1.1 Chain Initiation 10 2.1.2 Chain Propagation 13 2.1.3 Chain Termination 14 2.1.4 Chain Transfer 15 2.1.5 Polymerization Rate 17 2.1.6 Steady-State Analysis 18 2.2 Controlled/Living Radical Polymerization 19 2.2.1 Reversible Deactivation 20 2.2.2 Class of Reversible Deactivation Mechanism 24 2.2.3 Kinetic Consideration 26 2.3 Radical Polymerization in Heterogeneous Systems 30 2.3.1 Events in Heterogeneous Polymerization 31 2.3.2 Reaction Intervals in Emulsion Polymerization 34 2.3.3 Polymerization Rate in Heterogeneous System 35 iv 2.3.4 Compartmentalization 38 2.3.5 Class of Heterogeneous Polymerization 47 2.4 References 53 Chapter 3 Assessment of the Influence of Microwave 68 Irradiation on Conventional and Controlled/Living Radical Polymerization of Styrene 3.1 Abstract 69 3.2 Introduction 70 3.3 Experimental Section 71 Materials 71 Conventional Radical Polymerization and RAFT Polymerization of Styrene 72 Characterization 72 3.4 Results and Discussion 73 Conventional Radical Polymerization: Oil bath vs Microwave 73 Conventional Radical Polymerization: High Microwave Power (with Air 79 Cooling) Conventional Radical Polymerization: High Microwave Power (Without Air 81 Cooling) RAFT Polymerization: High Microwave Power (without Air Cooling) 81 Microwave-Induced Radical Generation? 87 Azo-initiator effectiveness to the whole kinetics 87 3.5 Conclusions 89 3.6 References 89 v Chapter 4 Validity Limits for the Zero-One Approximation 92 in Styrene Emulsion Polymerization 4.1 Abstract 93 4.2 Introduction 94 Smith-Ewart Theory for the Kinetics of Emulsion Polymerization 94 Establishment of Zero-One Approximation 95 Development of Zero-One Kinetics of Emulsion Polymerization of Styrene 97 Interest of the Validity of Zero-One Approximation on Large Particles 99 4.2 Experimental Section 100 Materials 100 Hydrodynamic Chromatography (HDC) 101 Synthesis of Seed Latex of Polystyrene 101 Interval III Seeded Emulsion Polymerization of Styrene 102 Dilatometry for Conversion Reading 103 Gravimetry for Conversion Reading 104 4.3 Results and Discussion 104 Interval III Seeded Emulsion Polymerization 104 The Constancy of 휌 and 푘 111 Change in 푐 during Interval III Emulsion Polymerization 113 Dependency of Zero-One Validity on 휌 and 푐 113 Estimation of the Maximum Particle Size for Zero-One Validity 114 vi 4.4 Conclusions 117 4.5 References 117 Chapter 5 Synergistic Effects of Compartmentalization and 121 Nitroxide Exit/Entry in Nitroxide-Mediated Radical Polymerization in Dispersed System 5.1 Abstract 122 5.2 Introduction 123 5.3 Model Development 125 Homogeneous System 125 Heterogeneous System 126 Model for Exit/Entry of Nitroxide 128 5.4 Results and Discussion 130 5.5 Conclusions 138 5.6 References 138 Chapter 6 Chain Transfer to Solvent in the Radical 144 Polymerization of N-Isopropylacrylamide 6.1 Abstract 145 6.2 Introduction 146 6.3 Experimental Section 147 Materials 147 Measurements 148 vii General Polymerization Details 149 Conventional Radical Polymerization 149 Chain Transfer to Solvent (Mayo Plot) 149 Nitroxide-Mediated Polymerizations 150 Thermal Polymerization in the Absence of Initiator and Nitroxide 150 6.4 Results and Discussion 151 Limiting Molecular Weight 151 Conventional Radical Polymerization in DMF 151 Nitroxide-Mediated Radical Polymerization 152 Chain Transfer to Solvent/Monomer 156 Estimation of 퐶tr,S via Mayo Plot 161 Number of New Chains 162 Molecular Weight Distribution 164 Effect of Poly(acrylate) Macroinitiator 164 Spontaneous Initiation 165 Comparison with Literature 167 6.5 Conclusion 168 6.6 References 169 Chapter 7 Conclusions and Future Perspectives 175 Appendix 181 viii List of Figures Figure 2.1.

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