Fluorescence Monitoring of Cationic Photopolymerizations - Divinyl Ether Polymerizations Photosensitized by Anthracene-Derivatives

Cationic photopolymerizations of vinyl ethers were investigated using in situ, time-resolved fluorescence spectroscopy. Due to its short intrinsic time scale, fluorescence spectroscopy provides a means to characterize these polymerizations which are too rapid to be monitored by traditional methods. The fluorescence intensity of the photosensitizer (anthracene or its derivatives) was monitored as a function of time with spectra collected in intervals as short as 2 ms. An observed reduction in fluorescence intensity was attributed to consumption of the photosensitizer, providing a means to monitor the production of active cationic centers. The reaction rate increased as the initiator or photosensitizer concentrations were increased. Also, reactions photosensitized by anthracene and 9, 10-dimethylanthracene produced the fastest rates, followed by 9-vinylanthracene. The polymerization rate for 9,10-diphenylanthracene was considerably slower due to steric hindrance or resonance effects. These results illustrate the tremendous potential of in situ, time-resolved fluorescence spectroscopy for monitoring polymerizations.