Highly Crystallized Brilliant Polymeric Photonic Crystals via Repulsion-Induced Precipitation Assembly toward Multiresponsive Colorimetric Films

The construction of high-quality 3D polymeric photonic crystal (PC) films featuring fascinating tunable optical properties in a facile and time-efficient way remains a major concern. Herein, the rapid assembly of highly crystallized brilliant flexible 3D polymeric PC films and their application for multiresponsive colorimetric sensing are demonstrated. Monochromatic PC films with remarkably distinct structural color, narrow half-band width (27 nm), and broad tunability of band-gaps (from blue to red) are generated within seconds from highly concentrated and charged colloids (51 vol%, −57.6 mV) embedded in poly(N-isopropylacrylamide) matrix. A repulsion-induced precipitation assembly is found to be responsible for the ultrafast formation of close-packed PC colloidal arrays. Besides, the resultant PC films exhibit ultrasensitive and fast response to external stimuli, revealed by interesting droplet diffusion experiments. Thus these PC films can serve as efficient colorimetric sensing materials to visually determine diverse species including trace ionic strength (2.9 ppm), minor surfactant (1 × 10⁻³m), alcohol, and pH variation (1.0–13.9). (Figure presented.).