Study of Kinetics and Macroinitiator Efficiency in Surface-Initiated Atom-Transfer Radical Polymerization

Abstract

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.

Influence of Graft Density on Kinetics of Surface-Initiated ATRP of Polystyrene from Montmorillonite

“…2,3 In more recent years, researchers have realized the potential for utilizing ATRP to modify the surface chemistry of many materials. Colloidal silica, 4 montmorillonite clay (MMT), 5 gold films, [6][7][8] and silicon wafers [9][10][11] have been the most frequently studied substrates for surface-initiated (SI)-ATRP, where the first is a spherical particle and the last three are high-aspect-ratio materials.…”

“…These termination effects may be circumvented through the introduction of excess Cu II X 2 or unbound initiator at the onset of polymerization. 20 There is some evidence of the living character of SI-ATRP reactions depending on the monomer; for example, a number of reports indicate linear monomer conversion versus time in poly(methyl methacrylate) (PMMA), 8,11 whereas R p plateaus in polymerizations of poly(N-isopropylacrylamide), 7 polyacrylamide, 9 or poly(glycidyl methacrylate) (PGMA). 8 The role of graft density, F g , on R p is unclear.…”

Hierarchically Ordered Montmorillonite Block Copolymer Brushes

“…69,70 In more recent years researchers have realized the potential for utilizing ATRP to modify the surface chemistry of many materials. Colloidal silica, 71 montmorillonite clay (MMT), 72 gold films, [73][74][75] [76][77][78] have been the most frequently studied substrates for surface initiated (SI)-ATRP, where the first is a spherical particle and the last three are high aspect ratio materials.…”

“…These termination effects may be circumvented through the introduction of excess Cu II X 2 or unbound initiator at the onset of polymerization. 87 There is some evidence that the living character of SI-ATRP reactions depends on the monomer; for example, a number of reports indicate linear monomer conversion vs. time in poly(methyl methacrylate) (PMMA), 75,78 whereas R p plateaus in polymerizations of poly(N-isopropylacrylamide), 74 polyacrylamide, 76 or poly(glycidyl methacrylate) (PGMA). 75 The role of graft density, ρ g , on R p is unclear.…”

Monte Carlo simulation on kinetics of batch and semi-batch free radical polymerization

“…[13][14][15] Genzer and coworkers combined Monte Carlo motion with reaction mechanism using a probability of choosing motion or reaction and studied controlled radical polymerization in bulk and on flat surfaces. [16][17][18][19][20] He and coworkers studied self-condensing vinyl hyperbranched polymerization using modified Monte Carlo simulation method based on 3D bond fluctuation lattice model. [21][22][23] Using the same bondfluctuation model, Lattuada and coworkers studied the kinetics of free-radical cross-linking polymerization and compared Monte Carlo simulation with experimental and numerical studies.…”