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Controlled Radical Polymerization in the Dispersed Phase CONTROLLED RADICAL POLYMERIZATION IN THE DISPERSED PHASE by MARY E. THOMSON A thesis submitted to the Department of Chemical Engineering in conformity with the requirements for the degree of Doctor of Philosophy Queen's University Kingston, Ontario, Canada December, 2010 Copyright c Mary E. Thomson, 2010 Abstract Controlled radical polymerization (CRP) has emerged as a powerful method of creating polymers with tailored molecular architectures under mild reaction conditions. However, production of these polymers efficiently at an industrial scale will likely require them to be synthesized in the dispersed phase. Three types of CRP are explored, Atom Transfer Radical Polymerization (ATRP), Nitroxide Mediated Polymerization (NMP) and Catalytic Chain Transfer (CCT) to elucidate the intricacies of creating these novel polymer colloids. Compartmentalization in an ATRP dispersed phase system is explored theoretically to understand the effects of particle size and catalyst concentration on the polymerization. The results suggest that there is an optimal range of particle sizes where the rate of poly- merization is greater than that in an equivalent bulk system while maintaining both a lower PDI (polydispersity index) and higher livingness. All three factors are desirable in ATRP but generally cannot be achieved simultaneously in bulk. Compartmentalization manifests itself differently in CCT dispersed phase systems, where the segregation of the CCT agents into different polymer particles leads to multimodal molecular weight distributions. Control over the particle size is notoriously difficult for nitroxide mediated polymeriza- tion, as it is challenging to decouple an increase in the particle size with an increase in target molecular weight using a two stage emulsion polymerization approach. This often leads to colloidally unstable latexes for low molecular weight, high solids conditions which are the result of superswelling. We offer several strategies to minimize this problem and create colloidally stable, high solids, n-butyl acrylate latexes by NMP with moderate to high molecular weight targets (>70 kg·mol−1). Using this synergy between target molecu- lar weight and particle size, high solids (>40 wt.%), high molecular weight (<200 kg·mol−1) microemulsions (∼20 nm) of methyl methacrylate-co-styrene were prepared. Finally, the monomer type and nucleation mechanisms also play a role in determining the particle size distribution in NMP emulsion systems. Using n-butyl methacrylate in emulsion with surfactant concentrations above the critical micelle concentration yields latexes with bimodal particle size distributions. However a surfactant-free approach allows monomodal latexes to be created. i Statement of Co-Authorship All of the material presented in Chapters 3, 4 and 7 have been accepted and published in Macromolecules, a refereed journal. The material presented in Chapter 6 has been submitted to Macromolecules. The bulk of the research was carried out independently by myself, under the supervision of Dr. Michael Cunningham. The work in Chapter 4 was done in close collaboration with Dr. Niels Smeets, and the simulations demonstrated there were undertaken based on Dr. Smeets' previously published experimental work. He assisted in defining the scope of the project and played a large role in the revision of the manuscript. Dr. Jason Ness, of Arkema, Inc., provided technical guidance for the work presented in Chapter 5. Anna Manley, and undergraduate student, performed some of the preliminary experiments, under my supervision, for the work presented in Chapter 7. The preparation and editing of the aforementioned manuscripts and of this thesis was conducted under the supervision of Dr. Michael Cunningham. ii Acknowledgments I would like to thank Dr. Michael Cunningham for his guidance, encouragement, support and enthusiasm in working towards my PhD here at Queen's. I have had wonderful op- portunities for learning, development, travel and great experiences over the past four plus years. I would also like to thank my great friends Nicky, Niels, Jordan, Ula and Mikey for lots of fun and memories both in the lab and out. Thanks to the rest of the polymer group and the other graduate students in Chem. Eng. for discussions and great times too! Thanks also to all my friends, family and loved ones for their support throughout all of this. Over the years I have had the opportunity to work in collaboration with others, including Dr. Niels Smeets from Queen's and Eindhoven, Dr. Ale Butt´efrom ETH in Zurich (who taught me Fortran!), Dr. Jason Ness at Arkema and Anna Manley. Thank you to everyone! iii Table of Contents Abstract i Statement of Co-Authorship ii Acknowledgments iii Table of Contents vii List of Tables viii List of Figures x Nomenclature xi List of Publications xiv Chapter 1 Introduction 1 1.1 Overview . 1 1.2 Research Objectives . 3 1.3 Summary of Original Contributions . 3 Chapter 2 Background and Literature Review 5 2.1 Aqueous Dispersed Phase Polymerization . 5 2.1.1 Modeling of Emulsion and Miniemulsion Systems . 8 2.2 Controlled Radical Polymerization . 10 2.2.1 Nitroxide Mediated Polymerization . 11 2.2.2 Atom Transfer Radical Polymerization . 13 2.2.3 Catalytic Chain Transfer . 16 2.3 Controlled Radical Polymerization in the Dispersed Phase . 17 2.3.1 Dispersed Phase Nitroxide Mediated Polymerization . 17 2.3.2 Dispersed Phase Atom Transfer Radical Polymerization . 20 2.3.3 Dispersed Phase Catalytic Chain Transfer . 21 2.3.4 Compartmentalization in Controlled Dispersed Phase Polymerizations 22 2.3.5 Modeling of Compartmentalization in Controlled Systems . 25 References . 26 Chapter 3 Compartmentalization Effects on the Rate of Polymerization and the Degree of Control in ATRP Aqueous Dispersed Phase Polymerization 32 Preface . 33 iv TABLE OF CONTENTS Abstract . 34 3.1 Introduction . 35 3.2 Model Development . 38 3.2.1 Compartmentalized Model . 38 3.2.2 Bulk Polymerization Model . 41 3.2.3 Choice of Polymerization System . 42 3.3 Results and Discussion . 43 3.3.1 Rate of Polymerization and the Degree of Control . 43 3.3.2 Effect of the Targeted Degree of Polymerization . 48 3.3.3 Effect of the Catalyst Concentration . 51 3.4 Conclusions . 54 Acknowledgments . 55 References . 55 Chapter 4 Catalytic Chain Transfer Mediated Emulsion Polymerization: Compartmentalization and Its Effects on the Molecular Weight Distribution 57 Preface . 58 Abstract . 59 4.1 Introduction . 60 4.2 Theoretical Background . 62 4.2.1 Model Assumptions . 62 4.2.2 Kinetic Scheme . 64 4.2.3 Development of Population Balances . 67 4.2.4 Development of the Numerical Solution . 69 4.3 Results and Discussion . 70 4.3.1 Validation of the Model . 70 4.3.2 Effect of the Apparent Rate Coefficient of Catalytic Chain Transfer 72 4.3.3 Particle Size and the Confined Space Effect . 76 4.3.4 Changes in the Average Number of CCTA Molecules per Particle . 78 4.3.5 Changing the Diffusional Resistance to CCTA Entry and Exit . 80 4.4 Comparison of Simulations with Experimental Results . 82 4.5 Conclusions . 84 Acknowledgments . 85 References . 85 Chapter 5 Nucleation and Colloidal Characteristics of High Solids Ni- troxide Mediated Emulsion Polymerization of n-Butyl Acry- late with Di-BlocBuilder 88 Preface . 89 Abstract . 90 5.1 Introduction . 91 5.2 Experiment Section . 94 5.3 Results and Discussion . 95 5.3.1 1st Stage Conditions . 96 5.3.2 Changing Initiator Concentration to Target Different Molecular Weights 102 5.3.3 Surfactant Concentration . 106 5.3.4 High Solids Content Experiments with Varying Molecular Weights . 107 5.4 Conclusions . 112 Acknowledgments . 113 References . 113 v TABLE OF CONTENTS Chapter 6 High Solids Nitroxide Mediated Microemulsion Polymeriza- tion of MMA with a Small Amount of Styrene and the Syn- thesis of (MMA-co-St){block{(BMA-co-St) Polymers. 115 Preface . 116 Abstract . 117 6.1 Introduction . 118 6.2 Experimental . 120 6.3 Results and Discussion . 122 6.3.1 Evolution of the 1st Stage Latex . 122 6.3.2 Duration of the 1st Stage Polymerization . 126 6.3.3 Solids Content in the 1st Stage . 128 6.3.4 Effect of Initiator Concentration and Target Molecular Weight . 130 6.3.5 High Solids Microemulsion Polymerization . 135 6.3.6 Synthesis of Block Copolymers in Microemulsion . 137 6.4 Conclusions . 139 Acknowledgments . 140 References . 140 Chapter 7 Nitroxide Mediated Surfactant-Free Emulsion Polymerization of n-Butyl Methacrylate with a Small Amount of Styrene 143 Preface . 144 Abstract . 145 7.1 Introduction . 146 7.2 Experimental Section . 147 7.3 Results and Discussion . 149 7.3.1 Emulsion Polymerization with Surfactant Above the CMC . 150 7.3.2 Surfactant-Free Emulsion Polymerization . 153 7.4 Conclusion . 158 Acknowledgments . 159 References . 159 Chapter 8 Conclusions and Recommendations 161 8.1 Conclusions . 161 8.2 Recommendations for Future Work . 164 Appendix A Compartmentalization in Dispersed Phase ATRP 167 A.1 Equation Derivation . 167 A.2 Implementation of the Computer Simulation . 167 Appendix B Compartmentalization in Catalytic Chain Transfer 170 B.1 Kinetic Scheme for Free Radical Polymerization . ..
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