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Study of Structure-Function Relationships of Zwitterionic STUDY OF STRUCTURE-FUNCTION RELATIONSHIPS OF ZWITTERIONIC POLYMERS A Dissertation Presented to The Graduate Faculty of the University of Akron In Partial Fulfillment of the Requirement for the Degree Doctor of Philosophy Chen-Jung Lee May 2018 STUDY OF STRUCTURE-FUNCTION RELATIONSHIPS OF ZWITTERIONIC POLYMERS Chen-Jung Lee Dissertation Approved: Accepted: Advisor Department Chair Dr. Hongbo Cong Dr. Michael Cheung Committee Member Dean of the College Dr. Gang Cheng Dr. Donald P. Visco Jr. Committee Member Dean of the Graduate School Dr. Lingyun Liu Dr. Chand Midha Committee Member Date Dr. Jie Zheng Committee Member Dr. Xiong Gong Committee Member Dr. Yang Liu ii ABSTRACT This dissertation is to study the structure-property relationships of zwitterionic materials from the aspect of molecular level with integrating its antifouling ability into other functions including buffering ability, ionic conductivity and electronic conductivity. In the first project (chapter II), a tertiary amine-based polycarboxybetaine (PCB) were synthesized to compare with the conventional quaternary ammonium-based PCB in order to study how tertiary amine group affect the properties of the resulting polymer. Replacing quaternary ammonium with tertiary amine not only endowed this tertiary amine- based PCB with buffering capability at neutral condition, but also led to a weaker carboxylate that leads a less acidic buffering range. It was found that tertiary amine is favorable to obtain good lactone ring stability in switchable PCB materials. More importantly, the tertiary amine cation does not compromise antifouling properties of zwitterionic materials. In the second project (chapter III), three typical but structurally different zwitterionic materials, polycarboxybetaine, polysulfobetaine, and polyphosphorylcholine, were studied on their ionic conductivity along with other materials. Recently, zwitterions have shown its potential on enhancement of the ionic dissociation. To gain a better understanding on how immobilized zwitterionic functional group interact with the mobile ions in the solution, a series of polyelectrolyte hydrogels, including zwitterionic, cationic, iii anionic hydrogels, were examined and compared on their ionic conductivity and volume change in three types of salt solutions with various concentration. Zwitterionic hydrogels showed much higher ionic conductivity than that of the nonionic poly(ethylene glycol) methyl ether methacrylate hydrogel in all tested solutions. For both cationic and anionic hydrogels, the presence of mobile counterions led to high ionic conductivity in low salt solutions; however, the ionic conductivity of zwitterionic hydrogels surpassed that of cationic and ionic hydrogels in high salt solutions. In the third and fourth projects (chapter IV and V), zwitterionic sulfobetaine functional group was incorporated with poly(ethylenedioxythiophene) (PEDOT) to create a series of zwitterionic conjugated polymers, and the effect of sulfobetaine group on the conjugated polymer chain was studied. To address the challenge of the long-term stability in implantable bioelectronics, zwitterionic material with superior antifouling and conducting ability is highly desired for the interface between biological system and electronic system. Therefore, Poly(sulfobetaine-3,4-ethylenedioxythiophene) (PSBEDOT) was designed to combine the advantages of zwitterionic material and conjugated material. The PSBEDOT-coated surface exhibited low interfacial impedance, good cyclic stability and switchable antifouling/antimicrobial properties. In addition, two PSBEDOT derivatives with different spacer length, PSBEDOT-4 and PSBEDOT-5, were synthesized to compare with PSBEDOT to study how the zwitterionic sulfobetaine side group affects the reactivity of monomer and the properties of the resulting polymer. It was found that PSBEDOT-4 and PSBEDOT-5 showed significant improvement on interfacial impedance and cyclic stability without compromising antifouling properties. iv DEDICATION To my family and coffee, you are God’s gift to me. v ACKNOWLEDGMENTS First and foremost, I would like to express my deepest gratitude to my supervisor Dr. Gang Cheng for all the support and guidance. Without him, this dissertation would simply have not happened. I would like to thank all my committee members, Dr. Lingyun Liu, Dr. Jie Zheng, Dr. Xiong Gong, Dr. Yang Liu, and Dr. Hongbo Cong for their valuable advices. I would like to give my special thanks to my friends. It is my honor to have you guys accompany me along this long journey. All the happiness and sadness will be the best memory in my life. Last but not least, I must thank Haiyan Wu. All the memories of my PhD life have you inside. vi TABLE OF CONTENTS Page LIST OF TABLES ............................................................................................................... x LIST OF FIGURES ............................................................................................................ xi LIST OF SCHEMES ......................................................................................................... xiv CHAPTER ........................................................................................................................... 1 I. INTRODUCTION ............................................................................................................. 1 II. STRUCTURE-FUNCTION RELATIONSHIPS OF A TERTIARY AMINE-BASED POLYCARBOXYBETAINE .................................................................................... ….13 2.1 Introduction .............................................................................................................. 13 2.2 Experimental section ................................................................................................ 15 2.2.1 Chemicals. ........................................................................................................ 15 2.2.2 Synthesis of Monomers. ................................................................................... 16 2.2.3 Synthesis of Polymer Brushes via Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) ........................................................................................ 22 2.2.4 Synthesis of PCBMAA-1T, PCBMAA-2T, and PCBAA-1 ............................. 23 2.2.5 Molecular Weight Measurement of PCBMAA-1T, PCBMAA-2T, and PCBAA-1................................................................................................................... 23 2.2.6 Protein Adsorption Study ................................................................................. 24 2.2.7 Monomer and Polymer Titrations of CBMAA-1T, CBMAA-2T, and CBAA-1 ................................................................................................................................... 24 2.3 Results and discussion .............................................................................................. 25 2.4 Conclusion ................................................................................................................ 33 vii III. IONIC CONDUCTIVITY OF POLYELECTROLYTE HYDROGELS .................... 35 3.1 Introduction .............................................................................................................. 35 3.2 Experimental section ................................................................................................ 38 3.2.1 Chemicals ......................................................................................................... 38 3.2.2 Synthesis of the hydrogel ................................................................................. 39 3.2.3 Equilibrium water content assay ....................................................................... 39 3.2.4 The volume ratio of the hydrogels assay .......................................................... 40 3.2.5 Ionic conductivity assay ................................................................................... 40 3.3 Results and discussion .............................................................................................. 41 3.4 Conclusions .............................................................................................................. 54 IV. ELECTROACTIVE POLY(SULFOBETAINE-3,4- ETHYLENEDIOXYTHIOPHENE) (PSBEDOT) WITH CONTROLLABLE ANTIFOULING AND ANTIMICROBIAL PROPERTIES ....................................... 56 4.1 Introduction .............................................................................................................. 56 4.2 Experimental section ................................................................................................ 58 4.2.1 Chemicals and general instrumentation ............................................................ 58 4.2.2 Synthetic procedures ......................................................................................... 59 4.2.3 Electropolymerization of SBEDOT .................................................................. 62 4.2.4 X-Ray photoelectron spectroscopy (XPS) study .............................................. 63 4.2.5 Electrochemical characterization of PSBEDOT ............................................... 64 4.2.6 BAEC and NIH-3T3 cell adhesion study ......................................................... 65 4.2.7 Protein adsorption study – Surface Plasmon Resonance .................................. 66 4.2.8 Bacterial adhesion, antimicrobial and releasing study ..................................... 67 4.3 Results and discussion
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