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Synthesis of Polymer Nanoparticles Using SYNTHESIS OF POLYMER NANOPARTICLES USING INTRAMOLECULAR CHAIN COLLAPSE AND BENZOCYCLOBUTENE CHEMISTRY A Dissertation Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment Of the Requirements for the Degree Doctor of Philosophy Ajay Ramesh Amrutkar September 2016 i SYNTHESIS OF POLYMER NANOPARTICLES USING INTRAMOLECULAR CHAIN COLLAPSE AND BENZOCYCLOBUTENE CHEMISTRY Ajay Ramesh Amrutkar Dissertation Approved: Accepted: Advisor Department Chair Dr. Coleen Pugh Dr. Coleen Pugh Committee Chair Dean of the College Dr. Li Jia Dr. Eric Amis Committee Member Dean of the Graduate School Dr. Stephen Cheng Committee Member Date Dr. Mesfin Tsige Committee Member Dr. Alamgir Karim ii ABSTRACT Single chain polymer nanoparticle (SCPN) synthesis from different polymer precursors using benzocyclobutene (BCB) chemistry and intramolecular crosslinking was investigated in this study. Synthesis of highly fluorinated SCPNs from highly fluorinated uni-block copolymer precursor utilizing ‘pseudo-high dilution continuous addition technique’ was investigated. GPC confirmed selective intramolecular crosslinking and TEM images supported formation of sub-20 nm spherical polymer nanoparticles. Amphiphilic SCPNs prepared via step-wise crosslinking of an amphiphilic di-block copolymer chain were investigated for their morphology using 4 different characterization techniques: TEM, AFM, DLS and DOSY-NMR. TEM and AFM images showed presence of discreet SCPNs as loosely crosslinked coils that flatten out when deposited on the surface forming pancake like morphology with ≈ 20 nm sizes. All the techniques showed presence of bimodal size distribution of these nanoparticles in solution. A smaller sized distribution represented discreet SCPNs whereas larger sized (>40 nm) distribution represented physical aggregates of SCPNs. These aggregates were broken down upon significantly diluting the solution of nanoparticles (≤50 ng/mL). AFM analysis and water contact angle studies on thin films of amphiphilic SCPNs and polystyrene homopolymer blends proved that nanoparticles possess Janus-type morphology. In order to aid synthesis of SCPNs from block copolymer precursors, a new 2-component room temperature polymer crosslinking based on 1-acetoxyBCB containing polymers and a nucleophile was developed. Development of this system involved developing synthesis of new monomer (1-acetoxy-4 and 5-vinylBCB), synthesis of polymers containing this new monomer followed by optimization of their crosslinking reaction. Mechanism of crosslinking and structure of crosslinking unit formed for this crosslinking system was also identified. SCPNs were synthesized at room temperature from uni-block copolymer precursors using this new crosslinking system. Crosslinking reaction was characterized using 1H NMR, GPC and LS-GPC. Symmetric ABA tri-block copolymer precursors are proposed as precursors for synthesis of SCPNs of different morphologies employing intramolecular crosslinking. Initial results on synthesis of ABA tri-block copolymer containing highly immiscible blocks using chain extension approach is also reported. iii DEDICATION This thesis is dedicated to my parents, Mummy and Baba, for their sacrifices and unwavering support And In loving memory of my grandmother, Aai, her values and teachings remain very close to my heart iv ACKNOWLEDGEMENTS I would like to express my sincere gratitude to my advisor, Prof. Coleen Pugh, for giving me an opportunity to be a part of her research group despite my non-chemistry background. I would like to thank her for all the support, guidance and mentoring. I would also like to thank my committee members, Prof. Stephen Cheng, Prof. Li Jia, Prof. Mesfin Tsige and Prof. Alamgir Karim, for their guidance and help. I would also like to thank Prof. Ali Dhinojwala for giving me an opportunity to be a part of Akron’s polymer program in the year 2010. I would like to thank all the group members in the Pugh group for all the help and fun times in the lab. I was lucky to have an amazing mentor, Dr. Bill Storms, who taught me many new things. I would also like to thank Dr. James Baker, Isamu Ono and Liwen Xing for their help in BCB projects. Special thanks to Abhishek Banerjee, Gladys Rocío Montenegro-Galindo, Cesar Lopez, Colin Wright, Brinda Mehta, Nicole Swanson, Carolyn Scherger, Abby Freedman, Tyler Tommey and Dibyendu Debnath for their help. During the course of this work, I had an opportunity to collaborate with various researchers. I would like to thank Jacob Scherger (AFM), Dr. Fadi Haso (DLS), Dr. Jessi Baughmann (DOSY-NMR), Dr. Gary Leuty (Simulations) and Namrata Salunke (AFM on thin films). I have learnt many new things from each of them and their contribution has helped us gain more insight in our project. I consider myself fortunate to have been blessed with constant support of my teachers and mentors from my undergraduate education. I would like to express my sincere gratitude to Dr. Prakash Wadgaonkar (NCL, Pune), Dr. Shashank Mhaske (ICT, Mumbai) and Dr. Anagha Sabnis (ICT, Mumbai) for their support and inspiration. v Life in Akron would have been difficult without my friends. I would like to thank Kaushik Mishra for being an amazing roommate for 7 years. I would like to specially thank Kaushik Mishra, Nishad Dhopatkar, Dharamdeep Jain and Dr. Murthy Maddipatla for their help during my injury in 2012. I would also like thank Emmanuel Anim-Danso, Attila Gergely and family and Yeneneh Yimer and family for fond memories and lifelong friendships to cherish. My journey so far would have been impossible without the constant support of my family members. My parents, Mummy and Baba, remain the backbone of my life. Their sacrifices, positive encouragement and values keep me going ahead. My younger brother, Pavan, his maturity and understanding has been very crucial to my journey. My maternal grandparents, Aai and Bhau, remain a source of inspiration. My uncles and aunts have been very supportive during all my endeavors. I am extremely fortunate to have been born in a family where education is given utmost importance and support. I thank everyone from the bottom of my heart. vi TABLE OF CONTENTS Page LIST OF TABLES………………………………………………………………………………………………………………………................... xi LIST OF FIGURES…………………………………………………………………………………………………………………………………… xiii LIST OF SCHEMES…………………………………………………………………………………………………………………………………. xxi CHAPTER I. INTRODUCTION……………………………………………………………………………………………………………………. 1 II. LITERATURE REVIEW……………………………………………………………………………………………………………. 4 2.1 Benzocyclobutene (BCB) Chemistry………………………………………………………………………. 4 2.2 Single Chain Polymer Nanoparticles…………………………………………………………………….. 12 2.3 Atom Transfer Radical Polymerization………………………………………………………………… 18 III. EXPERIMENTAL METHODS………………………………………………………………………………………………… 27 3.1 Introduction……………………………………………………………………………………………………….. 27 3.2 Materials……………………………………………………………………………………………………………. 27 3.3 Techniques…………………………………………………………………………………………………………. 28 3.4 Synthesis of and studies on small molecules……………………………………………………... 30 3.5 Synthesis of polymers………………………………………………………………………………………… 37 3.6 Intermolecular crosslinking of polymers………………………………………………………….… 42 vii 3.7 Intramolecular crosslinking of polymers to synthesize single chain polymer nanoparticles……………………………………………………………………………………….. 44 IV. SYNTHESIS AND CHARACTERIZATION OF HIGHLY FLUORINATED SINGLE CHAIN POLYMER NANOPARTICLES……………………………………………………………………............................................. 48 4.1 Introduction ………………………………………………………………………………………………………… 48 4.2 Parameters responsible for selective intramolecular crosslinking using pseudo-high dilution continuous addition technique………………………………………………………………. 51 4.3 Synthesis of Highly Fluorinated Single Chain Polymer Nanoparticles…………………. 53 4.4 Characterization of Highly Fluorinated SCPNs using TEM……………………………………. 57 4.5 Conclusion …………………………………………………………………………………………………………. 60 V. CHARCATERIZATION OF AMPHIPHILIC NANOPARTICLES SYNTHESIZED VIA STEP-WISE CROSSLINKING OF A SINGLE DI-BLOCK COPOLYMER CHAIN……………………………………………… 61 5.1 Introduction………………………………………………………………………………………………………… 61 5.2 Transmission Electron Microscopy (TEM)…………………………………………………………….. 68 5.3 Atomic Force Microscopy (AFM) analysis of individual nanoparticles…………………… 77 5.4 Dynamic Light Scattering (DLS)…………………………………………………………………………….. 90 5.5 Diffusion-Ordered Spectroscopy Nuclear Magnetic Resonance (DOSY-NMR) …….. 98 5.6 Atomic Force Microscopy analysis of nanoparticles and polystyrene homopolymer blends………………………………………………………………………………………………………………… 104 5.7 Conclusions……………………………………………………………………………………………………….. 109 viii VI. DEVELOPMENT OF A NEW ROOM TEMPERATURE POLYMER CROSSLINKING SYSTEM BASED ON 1-FUNCTIONALIZED BENZOCYCLOBUTENE ……………………………………………….…… 111 6.1 Introduction ……………………………………………………………………………….…………………… 111 6.2 Problems with 1-ethoxy-4 and 5-vinylBCB……………………………………………….………… 113 6.3 Screening of potential 1-functionalized BCB-based molecules for room temperature crosslinking………………………………………………………………………………………………..……… 114 6.4 Synthesis of a new monomer/crosslinker: 1-acetoxy-4- and 1-acetoxy-5- vinylBCB……………………………………………………………………………………………..…………..…. 122 6.5 Synthesis of copolymers containing 1-acetoxyBCB………………………….….……………… 127 6.6 Intermolecular crosslinking of polymers containing 1-acetoxyBCB at room temperature…………………………………………………………………………………………………….. 134 6.7 Intramolecular crosslinking of polymers containing 1-acetoxyBCB at room temperature………………………………………………………………………………………………….…… 145 6.8 Conclusion………………………………………………………………………………………….………………
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