The effect of molecular weight on light scattering of photonic poly styrene-block-poly-2-vinyl pyridine nano-structure

Abstract

One dimensional structures often limit viewing angle as well as reflection color changes. We report a simple strategy to fabricate the ellipsoidal block copolymer nanoparticles, which have a wider viewing angle. The photonic crystals were made with the polystyrene-block-poly-2-vinyl pyridine(PS-b-P2VP) dispersed in chloroform. When the PS-b-P2VP was sonicated in polyvinyl alcohol(PVA), it became white emulsion. The photonic crystals were formed by self-assembly of block copolymers. We observed particle structure variations according to the difference in molecular weight, which were 52k-57k, 75k-66.5k, and 102k-97k. The swelling and nature of light scattering from structured particles changed by the addition of ethanol. The structure of the photonic crystals was investigated by the Transmission Electron Microscope and the color was measured by color-difference meter. The particles with low molecular weight showed the short wavelength reflection.