Post-Synthesis of Donor-Acceptor Stenhouse Adducts into Photochromic Microparticles

Encapsulating photoresponsive molecules into polymers is an effective strategy to achieve fast and efficient photochromism in the solid state. Water is often used as the dispersion phase for the formation of polymeric microparticles; however, it reacts with the photoresponsive molecules and induces irreversible structural degradation. In this work, we report a post-synthesis strategy to fabricate photochromic microparticles, where donor-acceptor Stenhouse adducts (DASAs) are applied as the photoresponsive molecules. Unlike direct loading, hydrostable precursors are loaded during the formation of polymeric microparticles, followed by synthesizing the DASAs inside the microparticles in a water-free environment. The photochromic microparticles are reversibly switched between colored and colorless states under the control of visible light irradiation and heat, while also exhibiting improved stability under hygrothermal conditions. Further applications of the photochromic microparticles as smart additives are demonstrated for controlling color-switching of bulk materials and rewritable photopatterning on surfaces. The post-synthesis approach is envisioned as a general strategy to fabricate microparticles with water-sensitive functional molecules.