Photopolymerization laser induced, kinetics

Most of the work reported so far on laser-induced photopolymerization deals with near UV and visible radiation ranging from blue (—400 nm) (3,12) to red light (—700 nm) (4). We present here a kinetic investigation on the... 

The objective of the present work was to determine the influence of the light intensity on the polymerization kinetics and on the temperature profile of acrylate and vinyl ether monomers exposed to UV radiation as thin films, as well as the effect of the sample initial temperature on the polymerization rate and final degree of cure. For this purpose, a new method has been developed, based on real-time infrared (RTIR) spectroscopy 14, which permits to monitor in-situ the temperature of thin films undergoing high-speed photopolymerization, without introducing any additive in the UV-curable formulation 15. This technique proved particularly well suited to addressing the issue of thermal runaway which was recently considered to occur in laser-induced polymerization of divinyl ethers 13>16. 

A critical and most important problem that still remained to be solved was to find an adequate analytical methcxl that would enable us to follow in real time the kinetics of such ultra-fast polymerizations. Different techniques have already been used to study the laser-induced curing of acrylic monomers (DSC, IR spectroscopy, interferometry,...) but none of them provide conversion versus exposure time curves for polymerization that occur in a fraction of a second. The results obtained by some of these techniques are now briefly reported for comparison with those obtained by using real-time infra-red (RTIR) spectroscopy, a powerful method newly developed in our laboratory to investigate the kinetics of ultrafast photopolymerizations (0. 

C. Decker, K. Moussa, A new method for monitoring ultrafast photopolymerizations by real-time infrared spectroscopy , Makromol. Chem., 1988,189, 2381-2394. C. Decker, K. Moussa, Real-time kinetic study of laser-induced pol5mierization , Macromolecules, 1989, 22, 4455-4462. 

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