Catalytic Dehydrogenation of Lauric Acid and a Potential Use in Polyester Synthesis

The substitution of depleting fossil resources by renewable resources is of paramount importance, especially for polymer chemistry with its large production volume, in order to guarantee a more sustainable future. Herein, a new three-step reaction sequence was developed to synthesize renewable fatty acid–based dimethyl esters from saturated fatty acids. The sequence consists of a catalytic dehydrogenation with molecular oxygen as oxidant, an esterification with methanol, and a dimerization reaction with dithiols via thia-Michael addition. Three new dimethyl esters were thus synthesized from lauric acid and fully characterized via infrared, ¹H NMR, and ¹³C NMR spectroscopy as well as mass spectrometry. Polyesters with molecular weights ranging from 26.0 to 31.8 kDa were obtained by polycondensation of each dimethyl ester with 1,12-dodecanediol. Methyl crotonate–based polymers were prepared for comparison with the fatty acid–derived materials. Thermogravimetric analysis revealed that the long side chains led to improved thermal stability, and differential scanning calorimetry showed side chain crystallization for one polymer.

Practical Applications Renewable dimethyl esters are valuable monomers for the sustainable synthesis of polyesters and polyamides. The herein-reported synthesis strategy valorized saturated fatty acids, a typically less useful resource for polymer chemistry.