| The general objective of this research is to provide a more thorough understanding of the reaction kinetics of cationic photopolymerizations. Photo-differential scanning calorimetry (PDSC) experiments will be performed to systematically characterize the effects on the rate of polymerization and the ultimate limiting conversion by a host of variables in reaction mixtures containing an epoxide monomer, which may have different number of epoxide rings in the monomer molecule. The variables are temperature, type and concentration of photoinitiator; type and concentration of photosensitizer, initiating light intensity, and finally monomer structure and functionality.; The rate of polymerization and the ultimate limiting conversion increase when the magnitude of the testing variable is increased; however, the relatively smaller increase in conversion may be attributed to the monomer structure and functionality. The reactivity of the three mono-epoxides investigated is as follows: phenyl glycidyl ether > butyl glycidyl ether > octyl glycidyl ether; but for conversion: PGE > OGE > BGE. With respect to monomer functionality, the reactivity is determined in this order: di-epoxides ≥ tri-epoxides > mono-epoxides; and for conversion: mono-epoxides > di-epoxides > tri-epoxides. Reaction conditions are 50°C, 52 mW/cm2, 8 mmolal initiator and 0.8 mmolal sensitizer. |
