Designing photonic crystals with ultranarrow stopband through spontaneous crystallization of polymeric colloids swollen by resin

Abstract

Photonic crystals are crystals in which the refractive index changes periodically. Photonic crystals reflect the light by forming a photonic band gap in which light with a specific wavelength cannot pass in a structure. When the band gap is in a visible light region, the photonic crystals become colored, and thus they have been attracting attention as materials that produce colors without using chemical pigments. Among the methods for artificially making photonic crystals, the formation of crystals through self-assembly of colloids has been used as a way to quickly and easily make wide-sized photonic crystals. The colloidal self-assembly mechanisms can be categorized based on the interactions between particles. Hard spheres without interactions which are affected by entropy, repulsive interactions, and attractive interactions are the methods, and all three methods have been used. Researches have been conducted mainly on silica particles dispersed in resin or water-dispersed polymer particles. Existing studies have the disadvantage of having a wide reflection graph because it is difficult to accurately control crystallization due to the characteristics of colloidal self-assembly. Therefore, in this study, polymer particles were dispersed in the resin to induce spontaneous crystallization through behavior of the swollen particles which are hard spheres, and films free of shear stress and having a narrow reflective spectrum was obtained