Patchy Micelles Based on Coassembly of Block Copolymer
Chains and Block Copolymer Brushes on Silica Particles
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Abstract
Patchy particles are a type of colloidal
particles with one or
more well-defined patches on the surfaces. The patchy particles with
multiple compositions and functionalities have found wide applications
from the fundamental studies to practical uses. In this research patchy
micelles with thiol groups in the patches were prepared based on coassembly
of free block copolymer chains and block copolymer brushes on silica
particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-<i>block</i>-poly(<i>N</i>-isopropylacrylamide) block
copolymers (PS-<i>b</i>-PNIPAM-SH and PS-<i>b</i>-PNIPAM-CIP) were synthesized by reversible addition–fragmentation
chain transfer polymerization and chemical modifications. Pyridyl
disulfide-functionalized silica particles (SiO<sub>2</sub>-SS-Py)
were prepared by four-step surface chemical reactions. PS-<i>b</i>-PNIPAM brushes on silica particles were prepared by thiol–disulfide
exchange reaction between PS-<i>b</i>-PNIPAM-SH and SiO<sub>2</sub>-SS-Py. Surface micelles on silica particles were prepared
by coassembly of PS-<i>b</i>-PNIPAM-CIP and block copolymer
brushes. Upon cleavage of the surface micelles from silica particles,
patchy micelles with thiol groups in the patches were obtained. Dynamic
light scattering, transmission electron microscopy, and zeta-potential
measurements demonstrate the preparation of patchy micelles. Gold
nanoparticles can be anchored onto the patchy micelles through S–Au
bonds, and asymmetric hybrid structures are formed. The thiol groups
can be oxidized to disulfides, which results in directional assembly
of the patchy micelles. The self-assembly behavior of the patchy micelles
was studied experimentally and by computer simulation