Biobased Ester 2‑(10-Undecenoyloxy)ethyl Methacrylate as an Asymmetrical Diene Monomer in Thiol–Ene Polymerization

In this work, a diene ester monomer, 2-(10-undecenoyloxy)­ethyl methacrylate (MHU), was synthesized by the enzymatic esterification of 10-undecenoic acid (derived from castor oil) and 2-hydroxyethyl methacrylate and employed in two different ways: (1) in thiol–ene polymerization with 1,4-butanedithiol (1,4-BDT) and (2) as a precursor in a Michael addition reaction with hexamethylenediamine. In thiol–ene bulk polymerization of the asymmetrical diene monomer MHU, which presents different reactivities for each double bond, higher molecular weights (up to 44.3 kDa) were reached when nonstoichiometric thiol–ene ratios were used. In the second approach, Michael addition allowed us to obtain a symmetrical diene monomer that was used to produce a polymer (11.3 kDa) containing both amine and ester groups by thiol–ene polymerization. Finally, for the same MHU/1,4-BDT molar ratio, miniemulsion thiol–ene polymerization resulted in higher molecular weights (up to 17 kDa) when compared with those from bulk polymerization (8.7 kDa).