Synthesis of pseudo-telechelic diols by transesterification and thiol-ene coupling

Transesterification of methyl esters of rapeseed oil with ethylene glycol in excess led to a ?-hydroxy fatty ester with a yield of 90%. 2-Mercaptoethanol was grafted onto the double bonds of this ?-hydroxy fatty ester by UV initiated thiol-ene coupling under mild conditions. Double bond conversion was found to be quantitative and yielded a polyol with average of two primary hydroxyl functions. This pseudo-diol was characterized by means of NMR spectroscopy, titration and mass spectroscopy (MS) and was used to synthesize polyurethane (PU) by step growth polyaddition with methylene diphenyl-4,4'-diisocyanate. The polymer, analyzed by thermogravimetric analysis (TGA) and DSC, showed a glass transition temperature of -3 degrees C, close to the one measured (8 degrees C) on a PU based on a commercial polyol, Desmophen 1150.