Synthesis of block copoly(styrene-b-p-nitrophenyl methacrylate) and its derivatives by atom transfer radical polymerization

The preparation of block poly(styrene-b-p-nitrophenyl methacrylate) (PSt-b-PNPMA) and its hydrolysis and amino substitution products, poly(styrene-b-methacrylic acid) (PSt-b-PMAA) and poly(styrene-b-N-butyl methacrylamide) (PSt-b-PBMAD), were described. Polystyrene macroinitiator (PSt-Br) with narrow molecular weight distribution (MWD; M-w/M-n = 1.18, M-n = 14 730) was prepared by ATRP using ethyl 2-bromobutyrate (EBB) as initiator and CuBr/2,2'-bipyridine(bpy) as catalyst. Then, (PSt-b-PNPMA)s were synthesized by ATRP of NPMA using PSt-Br as initiator and CuBr/bpy as catalyst. GPC and NMR studies showed that the plot of ln([NPMA](0)/[NPMA]) against polymerization time was linear, molecular weight (M-n) increased linearly with conversion, and the molecular weight distributions were narrow (1.26-1.38) and became narrower as M-n increased. PSt-b-PNPMA formed micelles in chloroform with PSt as shell and PNPMA as core but formed inverse micelles in dimethyl sulfoxide. PSt-b-PMAA and PSt-b-PBMAD were characterized by FTIR and NMR, but MWDs of PNPMA prepared by atom transfer radical polymerization were broad (M-w/M-n = 1.57-2.45). The difference between the copolymerization and homopolymerization of NPMA was discussed.