Title

Synthesis and Aqueous Solution Studies of Stimuli-Responsive Block Copolymers Synthesized by Reversible Addition-Fragmentation Chain Transfer Polymerization

Date of Award

2006

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Charles McCormick

Advisor Department

Polymers and High Performance Materials

Abstract

Among the living radical polymerization techniques, reversible addition-fragmentation chain transfer (RAFT) is arguably the most versatile processes in terms of the reaction conditions and monomer selection. Since the introduction of RAFT in 1998, McCormick and coworkers have employed the RAFT process to synthesize a wide range of water soluble (co)polymers with predetermined molecular weights, low polydispersities, and advanced architectures. However many academic and industrially important monomers, including vinylpyridines and acrylamido monomers, remain uncontrolled or poorly controlled by RAFT polymerization. Additionally, RAFT polymerizations have for the most part, been limited to high reaction temperatures. The overall goal of this research is to expand the scope of the RAFT process in terms of monomer selection and reaction conditions. This work may be divided into four sections. The first study concerns the first successful RAFT polymerization of both 2- and 4-vinylpyridine under bulk conditions. To this end cumyl dithiobenzoate (CDB) (73) was synthesized and subsequently employed to investigate the polymerization behavior of both monomers. The second study concerns the room temperature RAFT polymerization of NIPAM in N,N -dimethylformamide. The influence of [CTA] o /[I]o ratio on the rate of the polymerization and molecular weight distributions is investigated. Blocking experiments were also conducted to confirm high retention of chain end functionality. In the third study the ability to conduct RAFT polymerizations at room temperature is extended to aqueous media. The influence of temperature on the rate of polymerization and molecular weight control for both acrylamide (55 ) and N,N -dimethylacrylamide (DMA) ( 56 ) is investigated. The hydrolytic stability of the trithiocarbonate RAFT agent CMP (66 ) is also probed. The fourth study concerns the extension of aqueous room temperature RAFT conditions to include the less hydrophilic monomer NIPAM (57 ). The influence of [M]o /[CTA]o ratio and trithiocarbonate functionality on the rate of polymerization and molecular weight control is investigated. A series of di- and triblock copolymers of DMA (56 ) and NIPAM (57 ) were then synthesized in order investigate the aqueous solution behavior of these materials as function of temperature.