Sustainable Thiol-Ene-Itaconate Photopolymers with Tunable Dynamic Properties for 3D Printing

Abstract

Vegetable oils present a sustainable platform molecule for facile synthetic modifications to prepare monomers for vat photopolymerization additive manufacturing, yet the common use of (meth)acrylates for functionalization diminishes from their overall sustainability. Herein, this research turned toward the use of thiol-ene-itaconate polymerization by functionalization of epoxidized linseed oil using eugenol itaconate or cinnamyl itaconate monoesters. A small series of itaconate functionalized sugar-derived reactive diluents containing varied number of residual hydroxyl groups was developed to control and tailor dynamic transesterification and mechanical properties. Two unsaturated zinc bis(carboxylate) transesterification catalysts were also developed using biobased feedstocks with varied functionality and structural attributes to further tailor polymer properties. The polymers displayed efficient dynamic properties such as triple shape-memory and self-healing while also maintaining competitive mechanical properties by leveraging thiol-ene-itaconate crosslinking. Additionally, the cinnamyl groups were photoswitchable under 280 nm irradiation to modulate network crosslinking and hence stress relaxation kinetics. This research demonstrated that the efficient use of itaconate and natural ene unsaturation could be readily leveraged to yield acrylate-free 3D-printable materials with advanced properties.