Olefin cross-metathesis as a valuable tool for the preparation of renewable polyesters and polyamides from unsaturated fatty acid esters and carbamates†
Olefin cross-metathesis of unsaturated fatty acid methyl ester (FAME) derived benzyl carbamates with methyl acrylate is described. The obtained by-product, an α,β-unsaturated ester, was further modified via thia-Michael addition reactions in order to synthesize branched AA-type or AB-type monomers for the preparation of polyesters, which are tuneable by oxidation. Cross-metathesis of fatty acid derived carbamates was used as a novel approach to prepare linear AB-type monomers, which can be used for the preparation of renewable polyamides PA11, PA12 and PA15. The necessary fatty acid carbamates were prepared by applying a catalytic Lossen rearrangement procedure. The presented synthesis strategy has potential for the bio-sourced preparation of monomers for the production of polyamides. All prepared polymers were fully characterized by NMR, SEC, and DSC analyses. Additionally, the Young's modulus of the prepared long-chain polyamide PA15 was determined.