Large modulation of the bottlebrush diblock copolymer morphology and structural color through solvent selectivity.

Abstract

Bottlebrush block copolymers (BBCPs), characterized by densely grafted side chains along their backbone, have emerged as promising materials for structural color applications. Their unique architecture prevents entanglement and facilitates rapid assembly kinetics, enabling the formation of various photonic crystals with high tunability of structural color from the visible to the infrared range. However, accessing non-1D structures has been largely limited to synthetic approaches. In this paper, we report large modulation of a microphase separated morphology of the polystyrene-b-polylactide (PS-b-PLA) BBCP using a single material by exploiting selective solubility of the two blocks in a series of structurally similar solvents. Combining optical spectroscopy, electron microscopy, photoinduced force microscopy and X-ray scattering, we unveil the microstructural evolution as dependent on solvent selectivity. Furthermore, we uncovered the mechanisms underlying the differences in assembly, where highly selective solvents induce sidechain aggregation, altering the volume fraction and facilitating the formation of non-1D structures.