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Author ORCID Identifier

https://orcid.org/0000-0003-0768-6474

AccessType

Open Access Dissertation

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering

Year Degree Awarded

2019

Month Degree Awarded

May

First Advisor

Todd Emrick

Subject Categories

Biological and Chemical Physics | Materials Chemistry | Organic Chemistry | Polymer Chemistry | Statistical, Nonlinear, and Soft Matter Physics

Abstract

This dissertation describes the synthesis and characterization of novel monomers and (co)polymer zwitterions that incorporate trialkylsulfonium cations. The novel materials presented herein constitute a unique type of polymer zwitterions that exhibit salt- and temperature-dependent water solubility as well as inherent reactivity. The behavior of these polymers in aqueous solutions, as nanostructures, and at liquid-liquid interfaces was studied; in all cases, the inherent reactivity of the polymers was harnessed towards the fabrication of novel polymers and soft materials. Following an introductory chapter, Chapter 2 describes the synthesis of sulfonium sulfonate monomers and polymer zwitterions. Both styrenic and methacrylic monomers were synthesized on a multigram scale and polymers were prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization. Solution properties of the polymers were characterized and compared to analogous ammonium-based polymer zwitterions. Unlike conventional polymer zwitterions, the sulfothetin polymers described in Chapter 2 are inherently reactive and amenable to nucleophilic substitution, thus affording access to a diverse range of materials by post-polymerization modification. Chapter 3 presents the preparation of double zwitterionic diblock copolymers, composed of poly(phosphorylcholine methacrylate) (PMPC) and polymer sulfothetin styrene (PSTS) blocks. Polymers with different PSTS incorporation were prepared, and their self-assembly in aqueous environments was studied. Nanoscale self-assembled structures with sizes tailored by the length of the PSTS block were obtained when the diblock copolymers were dispersed in water. Increasing the salt concentration in the aqueous solutions triggered disassembly into unimeric structures, and the critical salt concentration at which disassembly occurred hinged on the degree of polymerization of the PSTS block. Additionally, we harnessed the reactivity of the PSTS block as a stimuli to trigger the self-assembly at high salt concentrations. Finally, Chapter 4 describes the preparation of polymer sulfothetin-stabilized oil-in-water emulsion networks that display salt-concentration-dependent adhesion, aggregation and rheological behavior. These emulsions were processed into supracolloidal fibers by extrusion into water reservoirs. The fibers underwent disaggregation upon increasing the salt concentration of their surroundings. Utilizing the methacrylic and styrenic polymer sulfothetins presented in Chapter 2 as emulsion stabilizers, allowed for tailoring the salt concentration required to trigger fiber disaggregation. Finally, the reactivity of the polymeric zwitterions towards thiolate nucleophiles in aqueous environments gave access to covalently crosslinked fibers that were stable to high salt concentrations.

DOI

https://doi.org/10.7275/14218813

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