ABSTRACT
The anionic block copolymerization of methyl methacrylate (MMA) and 2-(1-acetoxyethoxy)ethyl methacrylate (2) was first carried out by the sequential polymerization of MMA and 2, using (1,1-diphenylhexyl)lithium (DPHL) as the initiator, in the presence of LiCl ([LiCl]/[DPHL]0 = 4), in tetrahydrofuran (THF), at −60°C. The block copolymer obtained [poly(MMA-b-2)] possesses a controlled molecular weight, designed composition, and narrow molecular weight distribution (M w/M n = 1.05−1.13). Then, toluene, isobutyl vinyl ether (IBVE), and EtAlCl2 were added to the THF solution of poly(MMA-b-2) obtained during the previous step. Every side chain of the poly(2) segment of poly(MMA-b-2) could be activated by a Lewis acid, EtAlCl2, to initiate the living cationic polymerization of isobutyl vinyl ether at room temperature. The THF, which was used as the solvent in the preparation of poly(MMA-b-2), acted as a weak Lewis base which stabilizes the propagating carbocation in the cationic polymerization step of IBVE. In this manner, a block–graft copolymer consisting of poly(MMA-b-2) as the block backbone and poly(IBVE) as the side chains attached to the poly(2) segment was prepared. This copolymer has a designed graft number, controlled molecular weights of the backbone and side chains, and a narrow molecular weight distribution (M w/M n = 1.11−1.16). In a similar way, a star-shaped copolymer consisting of one poly(MMA) arm and several poly(IBVE) arms could be prepared, by restricting the polymerization degree 136of 2 to a small value during the preparation step of poly(MMA-b-2). This star-shaped copolymer also possesses a designed arm number, controlled molecular weight, and narrow molecular weight distribution (M w/M n = 1.10–1.20).
