Photopolymerization kinetic studies of UV-curable sulfur-containing difunctional acrylate monomers using photo-DSC

We synthesized UV-curable difunctional sulfur-containing thioacrylate and thiourethane acrylate with high refractive indices. The monomer structures were confirmed by nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The photopolymerization kinetics of 3,3′-thiobis(1-(phenylthio)propane-3,2-diyl) diacrylate (SMDA) and 4,12-dioxo-6,10-bis(phenylthiomethyl)-3,13-dioxa-8-thia-5,11-diazapentadecane-1,15-diyl diacrylate (SMUA) were investigated by photo-differential scanning calorimetry (photo-DSC). The effects of various parameters such as the UV intensity, temperature, photoinitiator concentration, and the type of initiator were evaluated. In SMDA, as the temperature and light intensity increased, the peak maximum time tended to decrease. The conversion increased with increasing temperature up to 60 °C and light intensity up to 20 mW/cm2. The highest polymerization conversion was achieved with a PI concentration of 2.5% (w/w) with BK-6 as the PI. In SMUA, the rate of photopolymerization reached to the maximum value at 60 °C and 20 mW/cm2. For the PI concentration, the maximum conversion and polymerization rate constant were the highest with 2.5% (w/w). Also the highest conversion of polymerization was achieved using HP-8 as the PI. The activation energies of SMDA and SMUA were 3.95 and 36.01 kJ/mol, respectively. Open image in new window