Synthesis of biobased and versatile monomers from itaconic acid and homocysteine thiolactone and their applications in step-growth and radical polymerization approaches

In the context of the development of fully bio-based materials, access to multi-functional bio-based monomers represents one of the primary industrial challenges in the upcoming years. Itaconic acid and N-acetyl homocysteine thiolactone are two promising sustainable building blocks displaying complementary reactivities. In this paper, we design new sustainable monomers, beta-N-homocysteine thiolactyl itaconamic acid and alpha,beta-N,N '-homocysteine thiolactyl itaconamide, by functionalizing itaconic acid with one or two thiolactone moieties by amidification reaction in water. These synthesized monomers are very versatile bearing both an activated vinyl group that can react through either radical or Michael addition mechanisms, and a thiolactone ring, which is prone to undergo nucleophilic ring-opening reaction with primary amines liberating a highly reactive thiol. The polymerizability of these two monomers was then examined according to two polymerization pathways. In a first stage, the step-growth polyaddition of both monomers according to an aminolysis-thiol-Michael addition mechanism was studied in the presence of various functional primary amines, leading to the preparation of original multi-functional oligopoly(amide-thioether)s. In a second stage, the chain-growth free radical (co)polymerization of both monomers was investigated and enabled the synthesis of COOH-containing and functionalizable polymethacrylates. All the monomer and (co)polymer structures were carefully characterized by 1H, 13C, COSY, and HSQC. Sustainable monomers were designed from itaconic acid and thiolactone. These monomers enabled the preparation of multi-functional polymers according to different pathways.