Date of Award

Fall 12-2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

Committee Chair

Dr. Charles McCormick

Committee Chair Department

Polymers and High Performance Materials

Committee Member 2

Dr. Stephen Boyes

Committee Member 2 Department

Polymers and High Performance Materials

Committee Member 3

Dr. Charles Hoyle

Committee Member 3 Department

Polymers and High Performance Materials

Committee Member 4

Dr. Robert Lochhead

Committee Member 4 Department

Polymers and High Performance Materials

Committee Member 5

Dr. Andrew Lowe

Committee Member 5 Department

Polymers and High Performance Materials

Abstract

Reversible addition-fragmentation chain transfer (RAFT) is arguably the most versatile living radical polymerization technique in terms of the reaction conditions and monomer selection. Since the introduction o f RAFT in 1998, McCormick and coworkers have employed the RAFT process to synthesize a w ide range o f water-soluble (co)polymers w ith predetermined molecular weights, low polydispersities, and advanced architectures. However, the controlled polymerization of important monomers, such as unprotected, chiral, amino acid based monomers, directly in water has yet to be reported. The incorporation o f these monomers into stimuli-responsive block copolymer ers w ill create novel polymer er systems that can be reversibly “locked” under facile conditions and have potential applications in sequestration and targeted delivery. Additionally, the controlled synthesis of (co)polymers based on chiral, amino acids d ire ctly in water can now be achieved and their chiroptical behavior investigated. The overall goal of this research is to utilize the RAFT process for the polym erization o f chiral, amino acid based monomers directly in water, to investigate the self-assembly behavior o f stim u l responsive block copolymers containing an amino acid based block, and to investigate the chiroptical properties o f enantiomeric (co)polymer based on the chiral, amino acid based monomers.

This work may be divided into four sections. The first section concerns the first successful RAFT polymerization o f an unprotected amino acid based monomer directly in water and its incorporation into thermally responsive block copolymers. TV-acryloyl Lalanine (A L A L ) (48) was synthesized and its polym erization behavior in the presence of the dithioester CTP (64) and the trithiocarbonate EMP (67) was investigated. B lock copolymers containing a hydrop hilic block of D M A (58), a cross-linkable block of A L A L (48), and a therm ally-responsive block of N IP A M (59) were subsequently synthesized, and the aqueous self-assembly behavior was investigated. The second section expands on the aqueous R A FT polymerization of an unprotected amino acid based monomer and its incorporation into dual responsive block copolymers. A -acryloyl L-valine (A V A L ) (50) was synthesized, and its polymerization behavior mediated by EMP (67) at both 30 °C and 70 °C was investigated. Block copolymers containing a hydrophilic block o f D M A (58) and a statistical block o f the thermally-responsive monomer N IP A M (59) and the pH-responsive monomer A V A L (50) were synthesized, and their aqueous self-assembly behavior was investigated. In the third section, the chiroptical properties of amino acid based (co)polymers were investigated. C hiral homo- and block copolymers based on the enantiomeric monomers A L A L (48) and TV-acryloyl D-alanine (A D A L ) (49) were prepared d ire ctly in water via R A FT polym erization. Enantiomeric homopolymers, block copolymers, and a statistical copolymer was synthesized, and the chiroptical a ctivity of these biomimetic polymer and their analogous model compounds was investigated. The fourth section details work done in collaboration w ith D r. Yuting Li and concerns the utilization of R A FT for the preparation o f shell cross-linked m icelles for potential applications in sequestration and targeted delivery. Thermally responsive micelles based on p o ly (ethylene oxide)-block-[(A ,A -dim ethylacrylamide)-5to t-(A - acryloxy succinimide)]-&/ocA:-(N-isopropyl acrylamide) triblock copolymer are synthesized and subsequently shell crosslinked with ethylenediamine or cystamine. When cystamine is used, fully reversible SCL micelles are formed.

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