Double-inverse-opal structured films of a hydrogel framework and mobile inorganic particles

Abstract

Double-inverse-opal (DIO) structured assemblies are three-dimensionally ordered porous materials containing core particles inside. In this work, DIO structured films composed of mobile inorganic colloidal particles within an organic polymer gel framework were developed. As the organic backbone, a poly(N-isopropylacrylamide) gel (PNIPAM gel) was employed to enhance the flexibility and processability of the films. A three-dimensional periodic structure of fluorescent-labelled silica core particles in the film was observed with confocal microscopy. Thermally induced volume transitions of the PNIPAM gels were observed, which showed the potential for stimuli-responsive optical materials. By selective etching of the sacrificial shell layers surrounding the core particles, cavities formed around the cores, and they exhibited random Brownian motion inside these pockets in the film. As a new type of organic-inorganic composite material, the proposed DIO structured films possessed unique characteristics originating from the combination of a flexible backbone and mobile cores, applicable to stimuli-responsive photonic devices, reusable catalytic particle assemblies, etc.