Visible Light-Mediated Photoclick and Thermally Reversible Furanic Dithioacetal Chemistry for Circular 3D Printing.

Photoclick chemistry has become essential for photocurable 3D printing due to its rapid, selective, and spatiotemporally controlled bond formation. Advancing toward circular manufacturing, however, requires photoclick systems that also enable thermally reversible bond cleavage for material recycling. To meet this requirement, we report a furanic dithioacetal-based photoclick platform that integrates visible-light-induced polymerization with intrinsic thermal reversibility. The monomers, derived from bio-based furanic aldehydes and thiols, are solvent-free liquids, ensuring homogeneous formulations well-suited for 3D printing. To address the spectral mismatch of conventional photocatalysts, a thioxanthone-based photoacid system is investigated, enabling efficient bond formation under visible light compatible with commercial digital light processing (DLP) printing. The resulting polymer networks exhibit tunable crosslinking densities, allowing precise control over mechanical properties. Crucially, the dynamic furanic dithioacetal linkages enable depolymerization of the printed materials into re-printable oligomers, with no loss of performance over multiple recycling cycles. This work establishes a chemically integrated strategy that unifies visible-light processability, solvent-free formulation, bio-based origin, and closed-loop recyclability, thus establishing a robust foundation for circular photopolymer platforms.