Novel mesoporous high-performance films derived from polycyanurate networks containing high-boiling temperature liquids

Novel mesoporous polycyanurate (PCN) films were generated by polycyclotrimerization of dicyanate ester of bisphenol E in the presence of varying amounts of inert high-boiling temperature liquids, i.e. dimethyl phthalate or dibutyl phthalate, followed by their quantitative extraction after complete formation of PCN crosslinked frameworks. The chemical structures of precursory networks and resulting porous thermosetting films were confirmed by FTIR analysis and gel fraction determination. The porosity of the latter films was examined by SEM and DSC-based thermoporometry. Average pore diameters were found to be lower than 50 nm and pore volumes as high as 0.16 cm3 g−1 were determined. The density values of porous samples were found to be lower than that of non-porous pure PCN synthesized as a model system, thus suggesting the occurrence of closed pore structures. Moreover, the thermal properties of PCN-based films were investigated by DSC and TGA. The high-boiling temperature liquids decreased their glass transition temperatures (Tg) and their degradation temperatures by acting as plasticizers. This plasticizing effect logically disappeared after removal of pore-forming phthalates from the networks: the Tg values of the mesoporous films were even higher than that of non-porous neat PCN, while their thermal stability turned out to be nearly identical to that of neat PCN.