Synthesis of well-defined alternating copolymers by controlled/living radical polymerization in the presence of Lewis acids

Several controlled/living radical polymerization (CRP) techniques (atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP), iodide degenerative transfer polymerization (IDTP), and reversible addition-fragmentation transfer polymerization (RAFT)) were studied for the alternating copolymerization of a donor monomer (styrene) and an acceptor monomer (methyl methacrylate or methyl acrylate) complexed with Lewis acid. RAFT polymerization was found to be the most versatile system. The combination of RAFT and Lewis acids complexation techniques allows synthesis of well-defined alternating copolymers poly(styrene-alt-methyl methacrylate) with controlled molecular weight (up to M-n = 70 000 g mol(-1)), low polydispersities (M-w/M-n < 1.3), and controlled comonomer sequences (similar to90% of alternating triads). These results were obtained in the presence of diethylaluminum chloride and ethylaluminum sesquichloride. Moreover, the alternating copolymers obtained in such copolymerizations retain chain end functionality and were used as macroinitiators for the synthesis of well-defined diblock copolymers poly(methyl methacrylate-alt-styrene)-b-polystyrene.