SYNTHESIS OF MONODISPERSE BLOCK COPOLYMERS CONTAINING METHACRYLIC-ACID SEGMENTS BY GROUP-TRANSFER POLYMERIZATION - CHOICE OF PROTECTING GROUP AND CATALYST

We have investigated the synthesis of block copolymers of n-butyl methacrylate with methacrylic acid, using group-transfer polymerization with three protected monomers. Use of trimethylsilyl methacrylate is restricted to polymers of low acid concentration, apparently because of competition between the monomer and the chain ends for available catalyst. Sequential polymerization with t-butyl methacrylate gave copolymers of narrow molecular weight distribution, which were converted to the acid-containing block copolymer by hydrolysis. Choice of catalyst is important and best results were obtained with different catalysts for the two monomers. There is some increase in polydispersity with chain length. Sequential polymerization of benzyl methacrylate with methyl methacrylate also gave good copolymers, with a single catalyst, which were converted to the acid-containing block copolymer by catalytic hydrogenation.