Initiation of RAFT Polymerization: Electrochemically Initiated RAFT Polymerization in Emulsion (Emulsion eRAFT), and Direct PhotoRAFT Polymerization of Liquid Crystalline Monomers

Abstract

We report on two important advances in radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization). (1) Electrochemically initiated emulsion RAFT (eRAFT) polymerization provides rapid polymerization of styrene at ambient temperature. The electrolytes and mediators required for eRAFT are located in the aqueous continuous phase separate from the low-molar-mass-dispersity macroRAFT agent mediator and product in the dispersed phase. Use of a poly(N,N-dimethylacrylamide)-block-poly(butyl acrylate) amphiphilic macroRAFT agent composition means that no added surfactant is required for colloidal stability. (2) Direct photoinitiated (visible light) RAFT polymerization provides an effective route to high-purity, low-molar-mass-dispersity, side chain liquid-crystalline polymers (specifically, poly(4-biphenyl acrylate)) at high monomer conversion. Photoinitiation gives a product free from low-molar-mass initiator-derived by-products and with minimal termination. The process is compared with thermal dialkyldiazene initiation in various solvents. Numerical simulation was found to be an important tool in discriminating between the processes and in selecting optimal polymerization conditions.