Synthesis and characterization of a high-temperature polycyanophosphate resin

A phosphorus-containing polymer with very high thermo-oxidative stability was synthesized for the first time by addition of silver nitrate to tricyanophosphine (P(CN)₃). By optimizing the reaction time and silver nitrate concentration to a 1:1 molar ratio, a new polycyanophosphate [p(CP)] was formed as the primary phosphorus-containing product over the competing species, P(CN)₃. The reactions and products were monitored by FT-IR, ICP-OES, NMR, and XPS spectroscopic techniques, which indicated a complicated oxidation reaction that converted the P(III) precursor species to P(V) polyphosphate species with pendant cyano- and isocyano- moieties. The p(CP) resin was found to contain a high (17.6 at.%) amount of phosphorus by ICP-OES, which contributed to its excellent thermo-oxidative resistance with a high char yield of over 60 wt.% at 1000 °C (1273 K) in air, indicating that the material could be particularly useful for high-temperature applications.