A new method for monitoring ultra‐fast photopolymerizations by real‐time infra‐red (RTIR) spectroscopy

Abstract An original method based on IR spectroscopy has been developed in order to follow real‐time photopolymerizations that take place in less than one second. Conversion versus time curves were directly recorded for various multiacrylic monomers irradiated in condensed phase, thus allowing an immediate evaluation of both the rate of polymerization and the amount of residual unsaturation in the UV‐cured polymer. This method proved well suited to study the effect on the polymerization rate of the photoinitiator efficiency, the monomer reactivity, the light intensity, the film thickness, and the O 2 inhibition. The dark polymerization that develops just after the UV exposure was investigated as a function of the degree of conversion and was shown to represent up to 60% of the total process. A comparison with other methods of kinetic analysis shows the unique advantages of real‐time infra‐red (RTIR) spectroscopy which permits to follow quantitatively and in situ ultra‐fast polymerizations.