Moisture-resistant protective films for UV-light filter based on diisocyanate-bridged polysilsesquioxanes

Three bridged silsesquioxanes were synthesized via the reactions between 3-aminopropyltriethoxysilane and three different diisocyanates, i.e., m-xylylene diisocyanate, 1, 6-diisocyanatohexane, and isophorone diiocyanate. The subsequent bridged polysilsesquioxane sols were prepared by the room-temperatured polycondensation of these bridged silsesquioxane using basic catalysis. Transparent films with a thickness of around 330 nm were obtained by dip-coating the bridged polysilsesquioxane sols on the nickel sulfate hexahydrate (NiSO4·6H2O, NSH) crystal wafers that are commercially used as ultraviolet light filter working at a wavelength of 300 nm. The N2 adsorption/desorption experimental results showed that the films were all nonporous with pore volume less than 2 × 10− 3 cm3 g− 1. The obtained three polysilsesquioxanes all exhibited very high condensation degree of siloxane (above 99%). These films showed high optical transmittance at desired wavelengths (280–320 nm) and excellent moisture-resistant protection to the NSH filters.