An Efficient Nonisocyanate Route to Polyurethanes via Thiol-Ene Self-Addition

A novel and efficient strategy for the synthesis of nonisocyanate polyurethanes has been developed via thiol-ene self-photopolymerization. An aliphatic thiol-ene carbamate monomer (allyl(2-mercaptoethyl)carbamate, AMC) was synthesized by a one-step synthesis procedure, from cysteamine and allyl chloroformate. The urethane group was therefore incorporated directly into the monomer precursor, avoiding the problems associated to toxic isocyanates. AMC was successfully stabilized with the radical inhibitor pyrogallol (1% wt). In addition, the use of phenyl phosphonic acid as coadditive allowed its stabilization for lower concentrations of pyrogallol (0.1% wt). AMC was directly transformed into thermoplastic polyurethane (TPU) through thiol-ene photopolymerization by UVirradiation at 365 nm. The obtained TPU presented semicrystalline nature and very high thermal stability (T-5% similar to 325 degrees C). It was found that high concentrations of pyrogallol decreased the reaction rate and final conversion of photopolymerization. (c) 2014 Wiley Periodicals, Inc.