Synthesis and development of bio-based UV-curable monomers and highly branched polymers from itaconic acid

Abstract

In this work, acrylic acid-based HBP and various monomers and polymers from itaconic acid have been synthesized and evaluated to gain a deeper understanding about the structure-properties relationship of UV-curing hyperbranched polymers. The focus was placed on the use of itaconic acid as it has the potential to be a bio-based alternative to acrylic acid for a range of UV-curing applications such as additive manufacturing, coatings or printing inks. Six acrylated HBP were synthesized and evaluated to determine the impact of each building block on the final properties. A novel simple synthesis pathway was developed that did not require the use of activated reagents leading to highly substituted materials while avoiding all gelation risk. The material showed higher reactivity towards UV-curing and higher mechanical and thermal properties than materials previously described. Novel building blocks from itaconic acid were developed using a simple and scalable process. Eight monoesters of itaconic acid were synthesized using simple and more complex cyclic alcohols. These monomers were reacted with a vegetable oil and the characterization of the resulting material showed that cyclohexyl itaconate was the most promising candidate. Hyperbranched polymers from itaconic acid were synthesized through different strategies. As simple esterification reactions lead to undesired side-reaction when the difunctional itaconic acid is used, several alternative pathways were investigated and are described. The most successful strategy involved the reaction of itaconic anhydride with a (branched) core followed by an end-capping reaction with an epoxide. Applying this strategy, 13 hydroxyalkyl terminated HBP_It were developed using a variety of core, generations and end groups. These promising materials exhibited good reactivity and properties and are good candidates to be used as UV-curable material or additive tougheners. Finally, novel reactive diluents from itaconic acid were synthesized, the first of their kind due to the challenging reactivity of itaconic and the lower intrinsic reactivity towards UV-curing. These monomers were found to greatly improve the viscosity, the reactivity, and the thermal and mechanical properties when mixed with UV-curing resins derived from itaconic acid.