Patchy Micelles Based on Coassembly of Block CopolymerChains and Block Copolymer Brushes on Silica Particles.

Patchy particles are a type of colloidalparticles with one ormore well-defined patches on the surfaces. The patchy particles withmultiple compositions and functionalities have found wide applicationsfrom the fundamental studies to practical uses. In this research patchymicelles with thiol groups in the patches were prepared based on coassemblyof free block copolymer chains and block copolymer brushes on silicaparticles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) blockcopolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition–fragmentationchain transfer polymerization and chemical modifications. Pyridyldisulfide-functionalized silica particles (SiO2-SS-Py)were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol–disulfideexchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were preparedby coassembly of PS-b-PNIPAM-CIP and block copolymerbrushes. Upon cleavage of the surface micelles from silica particles,patchy micelles with thiol groups in the patches were obtained. Dynamiclight scattering, transmission electron microscopy, and zeta-potentialmeasurements demonstrate the preparation of patchy micelles. Goldnanoparticles can be anchored onto the patchy micelles through S–Aubonds, and asymmetric hybrid structures are formed. The thiol groupscan be oxidized to disulfides, which results in directional assemblyof the patchy micelles. The self-assembly behavior of the patchy micelleswas studied experimentally and by computer simulation. [ABSTRACT FROM AUTHOR]