Characterization of photocurable networks in real-time and post-exposure

Several novel characterization techniques were developed to gain a molecular-level understanding of the effects of exposure intensity and exposure time on photopolymer network formation. These techniques enable detailed characterization of photopolymer behavior in real-time and post-exposure.

In situ dynamic mechanical analysis was performed to observe the changes in composite modulus during photopolymerization of thin acrylate films supported on stainless steel grid sheets. Vitrification phase transformations were monitored in real-time via remote sensing dielectric spectroscopy. The relationship between exposure intensity and vitrification time revealed the exposure conditions necessary to shift the crosslinking rate from reaction kinetics controlled to diffusion kinetics controlled.

The effect of exposure intensity and exposure time on chemical conversion was ascertained via Fourier transform infrared microspectroscopy mapping experiments. The relationship between exposure intensity and time at a given conversion level revealed an increased occurrence of radical isolation at higher conversions. Furthermore, the exposure necessary to maintain a fixed conversion indicated greater reciprocity failure at lower conversions, indicative of classical radical termination kinetics.