Macroporous organosilica films via a template-free photoinduced sol–gel process

Abstract

In the present work, we have designed a simple and original procedure for the spontaneous formation of macroporous organosilica films by photopolymerization-induced phase separation, avoiding the intervention of a template. The simple mixture of 3-(glycidyloxypropyl)trimethoxysilane (CH₃O)₃Si(CH₂)₃OCH₂-CHCH₂O (GPTMS), and poly(diethoxysiloxane) (C₂H₅O)₂SiO)_n (PDEOS, n ≈ 5), without solvent and water followed by UV illumination in the presence of a diaryl iodonium salt (photoacid generator) afforded macroporous hybrid films. This method relies on a single-step photoinduced sol–gel process with photogenerated Brønsted acids, resulting from the iodonium salt photolysis, which catalyse the hydrolysis–condensation reactions of both precursors. The formation of macropores was found to be strongly dependent on the concentration of PDEOS. It has been indeed proven that an increase in the fraction of PDEOS yielded macropores of increased diameters from 100 nm to 50 μm. In this study, our efforts have been focused on two essential aspects. On the one hand, the characterization of the macroporous films with regard to morphology, organic–inorganic microstructure and optical properties was commented upon thoroughly; on the other hand a general mechanism leading to the development of macropores was proposed and discussed.