Oxygen Tolerant and Room Temperature RAFT for Synthesizing Well-defined Polymer Architectures

A reversible addition-fragmentation chain transfer (RAFT) process was developed capable of being performed at room temperature and in the presence of oxygen by initiating polymerization through an alkylborane-amine complex. This air-stable alkylborane-amine complex was chemically deblocked with carboxylic acid or isocyanate functionalities to liberate a reactive alkylborane that consumes oxygen and generates radicals to drive the RAFT process. Alkylborane initiated RAFT (AI-RAFT) was demonstrated to allow a wide range of molecular weights to be targeted while maintaining narrow molecular weight distributions. In specific conditions, rapid polymerization was possible within minutes under an ambient environment, without any prior deoxygenation, yielding moderate monomer conversion and narrow dispersity polymer. Optimal conditions for conducting AI-RAFT were investigated with propionic acid and isophorone diisocyanate revealing that carboxylic acids require a larger excess of deblocker to alkylborane to promote high monomer conversion. The deblocker functionality was also observed to have an impact on polymerization kinetics, and in some cases, to influence the dispersity and achievable molecular weight. The retention of living chain-ends was confirmed by synthesizing block copolymers using AI-RAFT derived macro-chain transfer agents, which were found to most efficiently chain-extend when synthesized using lower concentrations of alkylborane initiator. In this thesis, a chemically induced RAFT process is introduced without requirement of any thermal, photochemical, electrical, or mechanical stimulus capable of polymerizing acrylamide, acrylate, and methacrylate monomers in limited amounts of oxygen at room temperature.M.S., Materials Science and Engineering -- Drexel University, 201