Graft, Block-Graft and Star-Shaped Copolymers by an in Situ Coupling Reaction

A tetrahydrofuran (THF) solution of the living poly(glycidyl methacrylate) (poly(GMA)) was prepared by the living anionic polymerization of GMA, using 1,1-diphenylhexyllithium (DPHL) as initiator, in the presence of LiCl ([LiCl]/[DPHL]0 = 3), at -45 degreesC. Upon introduction of a benzene solution of living polystyrene (poly(St)) into the above system at -30 degreesC, a very rapid coupling reaction between the epoxy groups of the living poly(GMA) and the propagating sites of the living poly(St) generated a graft copolymer containing a polar backbone and nonpolar side chains. When benzene solutions of living poly(St) and polyisoprene were sequentially transferred to the THF solution of living poly(GMA), a graft copolymer possessing two different nonpolar side chains was obtained. Further, a THF solution of the living block copolymer of methyl methacrylate (MMA) and GMA was prepared by the sequential anionic polymerization of the two monomers, at low temperatures. A block-graft copolymer having a poly(MMA-b-GMA) block backbone and poly(St) side chains was synthesized by reacting the living poly(St) with the epoxy groups of the above living block copolymer. In addition, when the poly(GMA) segment in poly(MMA-b-GMA) was short, a star-shaped copolymer containing a poly(MMA) arm and several poly(St) arms was obtained. GPC and 1H NMR measurements indicated that all the above copolymers possess high purity, designed molecular architectures, controlled molecular weights and narrow molecular weight distributions (Mw/Mn = 1.10-1.23).