Environmental‐Tolerant Ionic Colloidal Photonic Composites via Ion‐Dipole Interactions for Synchronized Optical‐Electrical Dual‐Response Underwater Flexible Sensing

Abstract Inspired by dynamic structural colors in nature, ionic colloidal photonic composites (ICPCs) offer synchronized optical‐electrical responses for advanced sensing applications. However, their practical deployment is hindered by environmental instability. Here, environmentally tolerant ICPCs with synchronized optical‐electrical dual‐response capabilities are developed. These ICPCs are fabricated by hot‐pressing poly (2,2,3,4,4,4‐hexafluorobutyl acrylate) (PHFBA)‐grafted silica colloidal particles doped with 1‐ethyl‐3‐methylimidazolium bis‐(trifluoromethylsulfonyl) imide ([EMIM] + [TFSI] − ) ionic liquid (IL), synthesized through surface‐initiated atom transfer radical polymerization. The resulting ICPCs exhibit well‐balanced mechanical properties, high ionic conductivity (≈10 −4 S m −1 ), and vibrant structural color. They demonstrate remarkable dual optical‐electrical response, with a mechanochromic sensitivity of 1.64 nm% −1 (≈80 nm wavelength shift) and a gauge factor of 1.05. The inherent hydrophobic PHFBA matrix, negligible IL vapor pressure, and robust ion‐dipole interactions between PHFBA's C─F bonds and [EMIM] + [TFSI] − 's imidazolium cations endow the ICPCs with exceptional environmental stability. These ICPCs maintain stable dual‐response performance under extreme temperatures (−25 °C and 100 °C), humidity variations (20% and 99% RH), and immersion in various media, including water, acidic/basic solutions (pH 1/13), seawater, and hexane for 14 days. As a proof‐of‐concept, the ICPCs function as underwater flexible sensors, providing real‐time optical‐electrical feedback for joint motion monitoring and Morse code communication, offering a versatile platform for smart wearable electronics.