Surface modification of a UV curable acrylate coating: In situ introduction of hydrophobic properties

Two polyfunctional silanes polymethyl-hydrosiloxane (I) and octakis(dimethylsiloxy)-T8-silsequioxane (II) are proposed as new co-initiators for radical acrylate photopolymerization reactions. In the presence of a type II photoinitiator such as benzophenone, isopropylthioxanthone or camphorquinone, these compounds are found reactive. The influence of oxygen is also examined. Incorporating only 1% (w/w) of I into an epoxy acrylate matrix allows the formation, under air, of a coating exhibiting a hydrophobic surface. In free radical promoted cationic polymerization, the addition of I to a BP/Φ2I+ system significantly enhances, under air, both the polymerization rate and the final conversion. The autoxidation reaction of I in the presence of BP under air generates a hydrophobic polymer surface. The reaction mechanisms are discussed on the basis of laser flash photolysis experiments.