Large‐Area Electrochromic Coatings: Composites of Polyaniline and Polyacrylate‐Silica Hybrid Sol‐Gel Materials

A low‐cost technique for fabricating large‐area electrochromic coatings is described. Polyaniline was incorporated into polyacrylate‐silica hybrid sol‐gel networks using suspended particles or solutions. A solution of polyaniline and poly[methyl methacrylate‐co‐3‐(trimethoxysilyl)propyl methacrylate] can be spray‐ or brush‐coated on transparent indium‐tin oxide substrates to form robust electrochromic coatings. Silane functional groups on the polyacrylate chain act as coupling and cross‐linking agents to improve surface adhesion and mechanical properties of the resulting composite coatings. These coatings showed reversible transparent to green color change when polarized at potentials between ‐0.4 and + 0.4 V vs. Ag/AgCl in a 0.2 M /acetonitrile electrolyte solution. The cycle lifetimes of polyaniline films were improved by incorporating the polymer in the polyacrylate‐Silica matrix. Electrochromic switching was demonstrated for the composite coatings in large‐area all‐solid‐state devices.