Fabrication of Patterned High-Density Polymer Graft Surfaces. 1. Amplification of Phase-Separated Morphology of Organosilane Blend Monolayer by Surface-Initiated Atom Transfer Radical Polymerization

Abstract

Patterned films of a low-polydispersity polymer densely end-grafted on a silicon substrate were fabricated for the first time by the combined use of the Langmuir−Blodgett (LB) and the surface-initiated atom transfer radical polymerization (ATRP) techniques: a blend monolayer of 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (CTS: ATRP initiator) and n-octadecyltrimethoxysilane (OTS: noninitiator) was immobilized on a silicon wafer by the LB technique, and then the ATRP of methyl methacrylate was carried out on the modified wafer in the presence of the Cu/ligand complexes. Atomic force microscopic studies revealed that the CTS/OTS blend was immiscible and phase-separated into two monolayer phases: most OTS molecules aggregate with each other, forming a condensed-type monolayer domain with CTS molecules excluded from there almost perfectly, and the remaining OTS molecules are incorporated in the matrix region. This 2-dimensionally phase-separated structure was successfully amplified by the controlled growth of a high-density graft layer only on the matrix phase of CTS as a main component. The amplification by the ATRP technique was characterized by a sharp boundary between the grafted and ungrafted domains; as a measure of the spatial resolution, the boundary sharpness Δw was evaluated to be ca. 100 nm. The domain size in the phase-separated structure was independent of the mole fraction of CTS, while it could be changed by changing the pH of the subphase water: namely, the higher was the pH, the larger was the domain size. It was deduced that a change in pH of the subphase water gave rise to a change in the hydrolysis rate of the methoxysilyl groups into silanol groups and hence a change in the rate of condensation of the silanol groups into domains.

Branched Fluoropolymer−Si Hybrids via Surface-Initiated ATRP of Pentafluorostyrene on Hydrogen-Terminated Si(100) Surfaces

“…42 For the surface-initiated ATRP, surface initiators were immobilized on an oxidized silicon surface, a hydrogenterminated silicon surface, or a monolayer-modified silicon wafer, usually in multistep processes. [34][35][36][37][38][39] More recently, highly branched cationic polyelectrolytes have been prepared by self-condensing atom transfer copolymerization. 43 In this work, linear, branched, and highly branched (arborescent) poly(pentafluorostyrene) (PPFS)-silicon (PPFS-Si) hybrids were prepared via surface-initiated ATRP from the 4-vinylbenzyl chloride (VBC) inimer and ClSO 3 H-modified VBC.…”

Tribological Properties of Poly(methyl methacrylate) Brushes Prepared by Surface-Initiated Atom Transfer Radical Polymerization

“…Practically, only 1 of 10 initiators bound to the surface is expected to initiate a polymerization because of the steric hindrance of the growing polymer, however, it is sufficient to afford a high-density brush. Atom transfer radical polymerization (ATRP) has been widely employed for the formation of polymer brushes because ATRP is compatible with various functionalized monomers, [8][9][10][11][12] and the living character of the ATRP process yields polymers with a low polydispersity. Many researchers are investigating the surface properties of tailored polymer brushes, 13 including adhesion, 14 chromatography, 15 biomaterials, 16 wettability, 17 and biocompatibility.…”

Silica‐supported biomimetic membranes

“…An outline of the system is summarized in Figure 2. It is a very early example of the SAM/LB combination done in the middle of 1980s, and this cencept is currently widely used by many researchers 34–50…”