| The UV cross-linking and gelation behavior of thiol-ene photopolymers were studied by utilizing in situ rheology and real-time Fourier transform infrared (FTIR) spectroscopy. The combination of these two techniques offers a powerful approach to investigate the changes in the material's macroscopic properties and chemistry during UV curing. The gel point properties of the photopolymers were also examined by applying the Winter-Chambon criterion. This criterion, in conjunction with rheology, allows for the accurate determination of the gel point and provides information on the material's properties at the gel point.;The first part of this study examines the effects of temperature and monomer functionality on the UV curing behavior of a model thiol-ene polymer. The cross-linking rate was found to be faster for higher temperatures and for the thiol-ene system containing the higher functional groups. Fractal dimensions at the gel point were also determined to be independent of temperature, indicating that the polymerization mechanism did not change over the temperature range studied.;The elastic modulus, obtained from in situ rheology, was also correlated with the thiol conversion, obtained from real-time FTIR spectroscopy. The elastic modulus did not have an appreciable value until the system reached its gel point, but increased very rapidly afterwards. In addition, the photoinitiated thiol-ene polymerization was determined to be a second order reaction. This was not consistent with the reaction order determined from the mechanisms suggested in literature. A new termination mechanism was then proposed to account for this discrepancy.;Finally, the effects of fumed silica fillers on the kinetics and gelation behavior of a model thiol-ene system were investigated. The fumed silica retarded the polymerization kinetics, but did not change the order of the reaction. The Winter-Chambon criterion was found not to be applicable for several filled systems. Consequently, a new method, which involved monitoring the critical strains, was suggested for determining the gel point of filled systems. |
