Controlling grafting density and side chain length in poly(n-butyl acrylate) by ATRP copolymerization of macromonomers

Atom transfer radical polymerization (ATRP) was used for the preparation and subsequent copolymerization of two acryloyl-terminated poly(n-butyl acrylate) macromonomers with different degrees of polymerization (DPnBA = 25 and 42). Homopolymerization of the higher molecular weight macromonomer (MM1; P(n)BA(42)-, M-n = 5600, DPMM = 42, M-w/M-n = 1.18) resulted in preparation of a densely grafted polymer with a narrow molecular weight distribution (M-w/M-n = 1.14), but with the limited degree of polymerization DP = 12. The ultimate degree of homopolymerization for the lower molecular weight macromonomer (MM2; PnBA(25)-A, M-n = 3400, DPMM = 25, M-w/M-n = 1.20) was higher, and DP increased from 12 to 22. The limited DP could be because of progressively increasing steric congestion for macromonomers in approaching the growing chain ends of densely grafted polymers. When MMs were copolymerized with nBA, the reactivity of MM was nearly the same as that of nBA monomer irrespective of the differences in the degree of polymerization of the MMs and the initial molar ratio of nBA to MM. Well-defined graft polymers with different lengths of backbone and side chains, and different graft density were successfully prepared by grafting through ATRP Tadpole-shaped and dumbbell-shaped graft polymers were also synthesized by ATRP. (c) 2006 Wiley Periodicals, Inc.