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 ω‐hydroxy fatty ester with a yield of 90%. 2‐Mercaptoethanol was grafted onto the double bonds of this ω‐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°C, close to the one measured (8°C) on a PU based on a commercial polyol, Desmophen 1150. Practical application: The products of the chemistry described in this contribution, i.e. polyol from vegetable oils derivatives, provide biobased building blocks for further PUs syntheses by reaction with diisocyanates. The obtained PUs are partially biobased and may be applied as binders and coatings.