Moisture-resistant protective film for KDP crystal based on bridged polysilsesquioxane

A novel bridged silsesquioxane with long bridging groups was synthesized with m-xylylene diisocyanate and 3-aminopropyltriethoxysilane. Bridged polysilsesquioxane sol was prepared by the sol-gel polycondensaion of as-synthesized bridged silsesquioxane under basic catalysis. Thin film was obtained by dip-coating the bridged polysilsesquioxane sol on the KDP crystal. 1H NMR was used to characterize the bridged silsesquioxane. 29Si MAS NMR and N2 absorption/desorption analysis were adopted to study the xerogel structure. The morphology of film was observed by AFM analysis. The moisture-resistance of film under relative humidity 60% for KDP crystals was studied. The laser-induced damage threshold(LIDT) of bridged polysilsesquioxane film at 355 nm and 1 064 nm was measured. The results show tha