Preparation and Proton Conductivity of Sulfonated Polymer-Modified Sintered and Self-Assembled Silica Colloidal Crystals

We prepared sintered self-assembled nanoporous silica colloidal crystals modified with poly(3-sulfopropyl-methacrylate) and poly(stryrenesulfonic acid) brushes covalently attached to the nanopore surface. The resulting robust membranes possess temperature and humidity-dependent proton conductivity of ∼2 × 10−2 S cm−1 at 30 °C and 94% RH, ∼1 × 10−2 S cm−1 at 85 °C and 60% RH, and water uptake of approximately 20 wt % at room temperature. We also prepared proton conductive membranes by self-assembly of silica nanospheres modified with poly(3-sulfopropylmethacrylate) and poly(stryrenesulfonic acid) brushes of different thickness. These membranes showed a slightly higher proton conductivity and water uptake but poor mechanical properties.