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The use of light to cure systems for applications ranging from protective coatings on floor tiles and optical fibers to coatings on compact discs has grown steadily since the first commercial uses were reported over fifty years 1 Virtually all free-radical photocurable systems today are based upon the following components: functionalized oligomers, monofunctional and multifunctional monomers to control viscosity and aid in development of the crosslinked networks, additives such as antioxidants and UV screeners which help protect the final cured films, and photointiators which absorb light and produce initiating radical species. The use of ultra-high light intensity sources that provide light at wavelengths corresponding to the absorption spectra of the photoinitiators ensure that the coatings are produced rapidly in the presence of air. While there have been many advances in the use of UV light to cure coatings rapidly in many environments, there are still many challenges that remain and opportunities for the future abound. Herein we highlight recent work from our lab on thiol-ene chemistry. Since thiol-ene curing is an extremely versatile chemistry that allows for free-radical curing in air, many potential applications are expected to emerge for its use. Thiol-ene polymerization is unique in that it is a step growth type polymerization that proceeds by a free-radical chain mechanism. In the mid 1970s, Morgan, Ketley and 24 showed that exposure of mixtures of multifunctional thiols and multifunctional enes resulted in crosslinked networks characterized by high functional group conversion. Applications included rapid printing processes and conformal coatings for electronic packaging. Two articles have reviewed all aspects of thiol-ene
photopolymerization.
