Well-defined graft copolymers containing a poly(methacrylate) backbone and functional or block poly(vinyl ether) side chains

Abstract

The anionic random copolymerization of methyl methacrylate (MMA) and 2-(1-acetoxyethoxy)ethyl methacrylate (AEEMA) was carried out using 1,1-diphenylhexyllithium (DPHL) as initiator, in the presence of LiCI ([LiCl]/[DPHL] 0 = 2), in tetrahydrofuran (THF), at -60°C. The resulting polymer, poly-(MMA-co-AEEMA), has a controlled molecular weight and a narrow molecular weight distribution (M w /M n = 1.05 ∼ 1.09). Without quenching, toluene, EtAlCl 2 and a functional monomer [2-acetoxyethyl vinyl ether (AcVE), 2-chloroethyl vinyl ether (CIVE) or 2-vinyloxyethyl methacrylate (VEMA)] were introduced into the above THF solution of the copolymer at 20°C. Every side chain of AEEMA unit of poly(MMA-co-AEEMA) was activated by EtAlCl 2 to induce the cationic polymerization of the functional monomer. THF, which was used as solvent in the preparation of the copolymer of MMA and AEEMA, acted as a Lewis base in the latter cationic polymerization, thus stabilizing the propagating site. By using this procedure, a controlled cationic polymerization of a functional monomer was achieved and a well-defined graft copolymer with functional side chains was obtained. Instead of a single functional monomer, the simultaneous addition of isobutyl vinyl ether (IBVE) and AcVE, CIVE or VEMA during the second step cationic polymerization process generated a graft copolymer with random copolymer side chains. Furthermore, a graft copolymer with block side chains could also be prepared by performing a block copolymerization during the second cationic grafting step by adding sequentially AcVE (CIVE or VEMA) and IBVE or vice versa. Every graft copolymer thus obtained possessed a high purity, controlled graft number and molecular weight as well as a narrow molecular weight distribution (M w /M n = 1.12 ∼ 1.25).