posted on 2020-06-03, 22:13authored byYingze Liu, Wangmeng Hou, Hanying Zhao
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 1H NMR, 13C 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-SiO2). 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-SiO2 and PEG-b-PS89, only spherical micelles are formed on
silica particles. At high BCP concentrations, Y-shaped polymer brushes
and PEG-b-PS143 chains coassemble into
surface wormlike structures on silica particles. In the coassembly
of PEG/PS-SiO2 and PEG-b-PS306, 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.