Polycaprolactone-Itaconic Acid Resins for Additive Manufacturing of Environmentally Degradable 3D and 4D Materials by Thiol-ene Photopolymerization.

Digital light processing (DLP) has emerged as a powerful tool for advanced manufacturing, enabling the fabrication of intricate 3D polymer structures and, more recently, responsive 4D architectures that adapt to environmental stimuli. However, current DLP technologies rely heavily on acrylate-based photocurable resins, which pose significant sustainability challenges from resin synthesis to end-of-life disposal. To address these issues, we present a novel solvent-free approach to functionalizing polycaprolactone (PCL) using biomass-derived itaconic acid (IA). The unsaturated moiety of IA enables efficient photopolymerization via thiol-ene chemistry in both dioxane and the sustainable solvent γ-valerolactone, affording excellent printability. In the resulting cross-linked networks, IA end-groups serve not only as photocurable sites but also as functional handles that confer environmental responsiveness, as demonstrated by pH-triggered 4D transformations and dye uptake. To simulate end-of-life conditions, we demonstrated hydrolysis and microbial degradation of the cross-linked materials in a sewage-derived inoculum, supporting the potential for biomass regeneration in a circular materials framework. This strategy provides a sustainable route to producing functional, mechanically robust resins for 3D and 4D printing, offering a reduced environmental impact without compromising performance.