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 int rinsic time scale, fluorescence spectroscopy provides a means to chara cterize these polymerizations which are too rapid to be monitored by t raditional methods. The fluorescence intensity of the photosensitizer (anthracene or its derivatives) was monitored as a function of time wi th spectra collected in intervals as short as 2 ms. An observed reduct ion in fluorescence intensity was attributed to consumption of the pho tosensitizer, providing a means to monitor the production of active ca tionic centers. The reaction rate increased as the initiator or photos ensitizer concentrations were increased. Also, reactions photosensitiz ed by anthracene and 9, 10-dimethylanthracene produced the fastest rat es, followed by 9-vinylanthracene. The polymerization rate for 9,10-di phenylanthracene was considerably slower due to steric hindrance or re sonance effects. These results illustrate the tremendous potential of in situ, time-resolved fluorescence spectroscopy for monitoring polyme rizations.