The photopolymerization of a diacrylate monomer with an N-aliphaticmaleimide as the photoinitiator has been investigated by photodifferential scanning calorimetry (photo-DSC), real-time infrared (RTIR) spectroscopy, and real-time UV (RTUV) spectroscopy. Photo-DSC exotherm results for relatively thick films (similar to 150 mu m) showed an increase in the polymerization reactivity (R) up to a concentration of only about 2 mol% N-aliphaticmaleimide. RTIR analysis was used to determine that the reactivity of a diacrylate thin film (similar to 10 mu m) increased continually as the concentration of AcOEMI increased from 0.1 to 30 mol%. Both RTIR and RTUV spectroscopy indicated that essentially AcOEMI was completely consumed in the polymerization process, and colorless crosslinked acrylate films with little absorbance above 300 nm were produced.