Synthesis of Poly(ST-co-COPSI)particles by soap-free emulsion copolymerization and its optical properties as photonic crystals

H.S. Choo, J.M. Ha, K.C. Lee
Gyeongsang national University, KR

Keywords: poly(ST-co-COPSI)particles, soap-free emulsion copolymerization, optical properties, photonic crystals


Highly charged, submicron-sized polymeric colloidal particles can self assemble into 3-dimentional(3D) opal structure which is useful template for photonic crystal. In this report, optical properties of poly[Styrene(ST)-co-Allyloxy-2-hydroxypropane sulfonic acid sodium salt(COPSI)] polymeric microspheres with number average diameters(Dn) determined by scanning electron microscopy within 200~380 nm size ranges by emulsifier-free emulsion polymerization were studied. By controlling the ST/COPSI ratio in the copolymerization and polymerization temperature, initiator and monomer concentration as well as divinylbenzene(DVB) crosslinker, monodisperse polymeric particles with various sizes were successfully prepared without complicated synthetic methods. Such submicron sized polymer colloids self-assembled into 3D opal structure exhibiting bright colors by reflection of visible light. The colloidal particles and the resulting opal structures were characterized by fiber optic Visible spectrometer with reflected light microscope, and the wavelength of the structural color from the colloidal crystal was conformed to have quantitative relationship with the size of colloidal particles as predicted by Bragg equation.