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 that the bridged polysilsesquioxane film exhibits excellent moisture-resistance for KDP crystal and relative high LIDT.