Hybrid UV-cured organic-inorganic IPNs

Hybrid organic-inorganic UV-cured coatings based on interpenetrating polymer networks (IPN) were prepared starting by an equimolar methacrylate-epoxy UV-curable mixture (bisphenol-A-diglycidyl dimethacrylate/bisphenol-A-diglycidyl ether, abbreviated as BisGMA/BADGE), in the presence of tetrafunctional silane monomer tetrakis(methacryloyloxy-ethoxy)silane (TetMESi) as inorganic precursor. The photocuring kinetics of the BisGMA/BADGE IPN monomer mixture were strongly affected by the order of the cure of the individual components. Addition of TetMESi resulted in higher degrees of reaction. DMTA of the BisGMA/BADGE IPN suggest a two phase structure. The rubbery modulus of the hydrolysed BisGMA/BADGE/TetMESi systems increased as the level of TetMESi was raised in the formulation due primarily to the significant reinforcing effect of the nano-silica particles. TGA of the BisGMA/BADGE IPN showed three degradation stages with no residual char but the hydrolysed BisGMA/BADGE/TetMESi systems formed a carbonaceous silica char which increased in mass as the level of TetMESi was raised. The two phase morphology of the BisGMA/BADGE IPN was confirmed by FE-SEM analysis. For IPNs prepared with TetMESi, SiO2 particles are evident in the FE-SEM image and have diameters in the nanometric size range.