Synthesis of Y-Shaped Polymer Brushes on Silica Particles and Hierarchical Surface Structures Fabricated by the Coassembly Approach

Abstract

Coassembly of polymer brushes and linear polymers in selective solvents provides a unique method for the fabrication of surface nanostructures on solids. However, some fundamental problems, including the effect of architecture of polymer brushes on the surface coassembly and the thermal dynamic process of the assembly, are left unsolved. To solve the fundamental problems, in this research we synthesized Y-shaped polymer brushes on silica particles and studied the coassembly mechanism of the Y-shaped polymer brushes and linear block copolymers (BCPs). Poly-(ethylene glycol)-block-polystyrene (PEG-b-PS) with a pyridyl disulfide group at the junction point (PEG-(SS-py)-PS) was synthesized by a combination of click chemistry, thiol−disulfide exchange reaction, and reversible addition−fragmentation chain transfer polymerization. The block copolymer and the precursors were characterized with 1 H NMR, 13 C NMR, size exclusion chromatography, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. PEG-(SS-py)-PS chains were anchored to the thiol-modified silica particles by the thiol−disulfide exchange reaction, and Y-shaped polymer brushes with PEG and PS arms were prepared on silica particles (PEG/PS-SiO 2 ). Coassemblies of PEG/PS Y-shaped polymer brushes and linear PEG-b-PS BCPs with different PS block lengths were studied. In THF/methanol mixtures (1/7, by volume), BCP chains and PEG/PS brushes can coassemble into surface structures. The PS block length and BCP concentration play key roles in the fabrication of surface structures. With an increase in PS block length, fewer BCP chains are organized onto the surfaces of silica particles due to the limited surface area. Different morphologies were observed in the coassembly of Y-shaped polymer brushes and linear BCPs. In the coassembly of PEG/PS-SiO 2 and PEG-b-PS 89 , only spherical micelles are formed on silica particles. At high BCP concentrations, Yshaped polymer brushes and PEG-b-PS 143 chains coassemble into surface wormlike structures on silica particles. In the coassembly of PEG/PS-SiO 2 and PEG-b-PS 306 , layered surface structures and fused vesicles are formed on silica particles. This research paves a new approach to the fabrication of hierarchical nanostructures on solid surfaces.

Homopolymer-Assisted Fusions of Polymer Brushes and Block Copolymer Vesicles

“…PEG 107 -b-PS 322 and PS 312 were synthesized by reversible addition−fragmentation chain-transfer (RAFT) polymerization. 33 The degrees of polymerization (DPs) of the polymers were determined by 1 H NMR. Based on size exclusion chromatography (SEC) results, the apparent number-average molecular weights and molecular dispersities of PEG 107 -b-PS 322 and PS 312 were determined to be 39.0 K and 1.29 and 32.8 K and 1.24, respectively.…”

“…PEG 107 - b -PS 322 and PS 312 were synthesized by reversible addition–fragmentation chain-transfer (RAFT) polymerization . The degrees of polymerization (DPs) of the polymers were determined by 1 H NMR.…”

“…Recently, we reported surface coassembly of “free” BCP chains and polymer brushes on silica surfaces. − Polystyrene (PS) brushes and poly­(2-(dimethylamino)­ethyl methacrylate)- block -polystyrene (PDMAEMA- b -PS) BCP chains are able to undergo surface coassembly into s-micelles on silica particles in a selective solvent . The driving forces for the surface coassembly are the miscibility of the PS blocks and PS brushes and the reduction of the surface energy.…”

Polymer brush-based erasable and rewritable nanostructured particle surfaces

“…Silica particles with pyridyl disulfide groups were prepared by using the method reported previously, 46,47 and PS brushes on the silica particles (SiO 2 -PS 80 ) were synthesized by thioldisulfide reaction between PS 80 -SH and pyridyl disulfide groups on the silica particles. The PS grafting density was around 0.6 chains per nm 2 .…”

“…In previous studies, we reported the fabrication of the nanostructured particle surfaces by coassembly of polymer brushes and free block copolymer (BCP) chains, and a variety of surface nanostructures, including spherical surface micelles, worm-like structures and layer surface structures, were fabricated. 43,46,47 Herein, we report the fabrication of the erasable and rewritable nanostructured particle surfaces formed by coassembly of polymer brushes and linear BCP chains. As shown in Scheme 1, the block copolymer of poly(ethylene glycol) (PEG) and polystyrene (PS) with a disulfide bond at the block point (PEG-SS-PS) is synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization.…”