Inorganic-organic hybrid polymers have been developed and tested for evaluation in optical and electrical applications. Although hybrid inorganic-organic polymers can be synthesized by sol-gel chemistry at first, the physical properties of hybrid inorganic-organic polymers are changed during thin film-making processes, that is, photocuring and thermal curing. To investigate the effect of photoinitiator on the material properties during processing, a model system containing methacrylic groups as organically polymerizable units was selected. The conversion of C=C double bond of methacrylic groups depending on some kinds of photoinitiator quantities was characterized by Fourier transform infrared spectroscopy. It was confirmed to correlate the degree of C=C double bond conversion with the refractive indices. Thermodynamically, the enthalpy of the photopolymerization of hybrid polymer was investigated by UV-DSC. UV-DSC spectra showed the exothermic nature of photopolymerization of ORMOCER(R) to be in dependence of photoinitiator quantities. (C) 2004 Wiley Periodicals, Inc.