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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).

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Acyclic triene metathesis (ATMET) polymerizations of linseed oil were performed in bulk and miniemulsion to evaluate the activity of different types of ruthenium-based catalysts (Grubbs 1st and 2nd generations, Hoveyda-Grubbs 2nd generation and Umicore M2) in both systems. Miniemulsion polymerizations with a nonionic surfactant resulted in polymer nanoparticles with an average size around 200 nm. The number-average molecular weight (Mn) of the polymers, approximately 6 kDa, obtained by linseed oil metathesis miniemulsion polymerizations was found to be comparable to linseed oil metathesis bulk reactions if Umicore M2 and Hoveyda-Grubbs 2nd generation catalysts and nonionic surfactants were used. The presence of oleic acid moieties and saturated fatty acids in linseed oil limited the molecular weight increase and cross-linking, since they act as chain-stoppers. On the other hand, ATMET homopolymerization of glyceryl triundec-10-enoate (UDTG) with terminal double bonds led to a massive gel formation due to the three highly reactive terminal double bonds per molecule. Increasing the amount of linseed oil in ATMET copolymerization between linseed oil and UDTG resulted in lower gel content.Practical applications Naturally occurring renewable plant oils as raw materials, without prior chemical modifications, are a very attractive alternative to fossil reserves. Linseed oil contains about 90% unsaturated fatty acids. This property makes it suitable for ATMET polymerization, including the miniemulsion technique, allowing the synthesis of branched macromolecular nanoparticles. The ratio of linseed oil and glyceryl triundec-10-enoate (UDTG) in ATMET copolymerization can tune the gel content, as the presence of oleic acid moieties and saturated fatty acids in linseed oil limits the cross-linking.