mz9b00721_si_001.pdf (2.52 MB)
Molecular Architecture Directs Linear–Bottlebrush–Linear Triblock Copolymers to Self-Assemble to Soft Reprocessable Elastomers
journal contribution
posted on 2019-11-01, 17:33 authored by Shifeng Nian, Huada Lian, Zihao Gong, Mikhail Zhernenkov, Jian Qin, Li-Heng CaiLinear–bottlebrush–linear
(LBBL) triblock copolymers
represent an emerging system for creating multifunctional nanostructures.
Their self-assembly depends on molecular architecture but remains
poorly explored. We synthesize polystyrene-block-bottlebrush
polydimethylsiloxane-block-polystyrene triblock copolymers
with controlled molecular architecture and use them as a model system
to study the self-assembly of LBBL polymers. Unlike classical stiff
rod-flexible linear block copolymers that are prone to form highly
ordered nanostructures such as lamellae, at small weight fractions
of the linear blocks, LBBL polymers self-assemble to a disordered
sphere phase, regardless of the bottlebrush stiffness. Microscopically,
characteristic lengths increase with the bottlebrush stiffness by
a power of 2/3, which is captured by a scaling analysis. Macroscopically,
the formed nanostructures are ultrasoft, reprocessable elastomers
with shear moduli of about 1 kPa, two orders of magnitude lower than
that of conventional polydimethylsiloxane elastomers. Our results
provide insights on exploiting the self-assembly of LBBL polymers
to create soft functional nanostructures.