Facile construction of dual bandgap optical encoding materials with PS@P(HEMA-co-AA)/SiO₂-TMPTA colloidal photonic crystals

An operable strategy for the construction of dual-reflex optical code materials from bilayer or Janus-structure colloidal photonic crystals (CPCs) has been established in this work. In this process, monodispersed submicrometer polystryene@poly(2-hydroxyethyl methacrylate-co-acrylic acid) hydrogel microspheres with soft-shell/hard-core structure and monodispersed colloidal silica spheres were fabricated. These two kinds of colloidal units can be facilely integrated into a single material without optical signal interference because they are well isolated for the immiscibility between water and ethoxylated trimethylolpropane triacrylate (TMPTA) and the upper layer of SiO₂-TMPTA is a kind of transparent. Moreover, diverse optical code series with different dual photonic bandgaps can be obtained via tuning the colloid sizes. Compared to the conventional single-reflex CPCs, the as-prepared dual-reflex optical code materials represented high information capacity in encoding process. More interesting, delicate code pattern has been also achieved on the optical film via the silk-screen printing technique, which will greatly extend the dual-reflex optical code materials to practical uses in areas containing bio-encoding, anti-counterfeiting, and flexible displays.