Morphologies and photonic properties of an asymmetric brush block copolymer with polystyrene and polydimethylsiloxane side chains

Abstract Asymmetric brush block copolymers (BBCPs) with polystyrene (PS) and polydimethylsiloxane (PDMS) side chains, g PS- b - g PDMS, were synthesized by ring-opening metathesis polymerization of corresponding norbornene macromonomers. The morphologies of the BBCP were systematically investigated with small-angle X-ray scattering and scanning electron microscopy. As the volume fraction of PS increases, the polymer self-assembles into spherical, cylindrical, and lamellar structures. Due to the shape asymmetry of the BBCP macromolecule, nanostructures with curved interfaces are easily formed. With a large d -spacing, most samples self-assemble into photonic crystals that selectively reflect ultraviolet light. Simulations have been conducted to calculate the photonic band structures of the two-dimensional photonic crystals. It is found that this system shows a wider partial band gap than other polymer systems with smaller refractive index contrast.