Structure manufacturing of proton-conducting organic-inorganic hybrid silicophosphite membranes by solventless synthesis

We have developed a new class of proton-conducting organic-inorganic hybrid silicophosphite membranes, produced by ethanol condensation of organically modified alkoxysilanes and anhydrous vinylphosphonic acid under solventless, catalyst-free, low-temperature, one-pot conditions. The membranes synthesized in this study are crack-free, large, and flexible, and they exhibit good thermal stability up to intermediate temperatures (∼218 °C). Structural analyses using ²⁹Si and ³¹P nuclear magnetic resonance spectroscopy and infrared measurements revealed that ethanol condensation produced an inorganic alternating copolymer structure, Si-O-P, with a phosphole group, and successive polymerization between vinyl and/or methacryl groups enabled these structures to connect with each other. In this way, it is possible to achieve structure manufacturing of inorganic-organic networks. The proton conductivities of the hybrids are as high as 5.2 × 10^-3 S/cm at 85 °C under 80% relative humidity.