Photoinitiating Systems for Hybrid Sol-Gel Coatings: Toward Enchanced Materials for UV-Curing Applications

Radiation curing in organic photopolymers has proved its value in terms of high technical performance with both ecological and economic advantages. Understanding and controlling the photochemical processes both in time and space represent the research in our Laboratory for more than twenty years. Nowadays, organic-inorganic sol-gel materials have gained special interest since theycombine the characteristics of glass and polymer and improve the properties of the final material. New horizons are thus opening for radiation curing of photopolymerizable hybrid organic/inorganic materials that are today very attractive for different applications such as coating technology, optics, sensors, catalysis... Although understanding of the photochemical step is of fundamental interest, little is known about the photochemistry in hybrid sol-gel medium. In this paper, Real Time Fourier Transformed Infra-Red spectroscopy was used to follow the photopolymerization of organic modified silicates upon UVirradiation. Various  hotoinitiating systems were tested for inducing radical polymerization of pendant polymerizable moieties anchored on the partially condensed silicate network. Experiments performed in both laminated and nonlaminated conditions allow to shed some light on unexplored aspects of the hybrid sol-gel photochemistry for coating applications. It provides new insights into photopolymerization processes of interpenetrating organic-inorganic networks leading to advanced materials.