Study of kinetics and macroinitiator efficiency in surface-initiated atom-transfer radical polymerization

Generation of surface-tethered block copolymer brushes with well-defined physicochemical characteristics requires achieving good control over the degree of polymerization of each block of the copolymer. In order to precisely form these block copolymer layers, one must (1) utilize a polymerization scheme that is capable of generating nearly monodisperse polymers, (2) fully characterize the kinetics of surface-initiated polymerization, and (3) produce macroinitiators with living characteristics capable of reinitiating the growth of each subsequent block. In this work, we describe technological steps leading to the controlled growth of surface-tethered homopolymers and multiblock copolymers via surface-initiated atom transfer radical polymerization (ATRP) from flat substrates. We first report on investigating the ability of a macroinitiator to reinitiate a homopolymer brush. We use computer simulations to illustrate the advantages of an "added deactivator" type ATRP over the traditional "sacrificial initiator" ATRP. In the section describing the formation of multiblock copolymer brushes we show that the growth of individual blocks in a multiblock copolymer brush depends on the type of macroinitiator and the type of monomer used to produce the subsequent block. We demonstrate that while poly(methyl methacrylate) and poly(2-hydroxyethyl methacrylate) form multiblock copolymer brushes readily (up to a hexablock reported herein), achieving good control over growth of surface-tethered multiblock copolymers comprising poly(methyl methacrylate) and poly(dimethylaminoethyl methacrylate) blocks with equal lengths of both blocks is challenging.