Caffeine-catalyzed synthesis of photopolymers for digital light processing†

Abstract

We report an elastic, degradable, and sustainable thiol–norbornene photopolymer for digital light processing. Caffeine, benign and bio-derived, catalyzes the in-tandem ring-opening reaction of cis-5-norbornene-endo-2,3-dicarboxylic anhydride and propylene oxide by alcohol-terminated polycaprolactone and produces the polymer at a 90 g scale. The synthesis tolerates moisture and adheres to green chemistry principles. The product doesn't require purification; mixing it directly with thiol cross-linkers and photo-additives affords the thiol–norbornene photopolymer. Digital light processing converts the photopolymer into high-fidelity prints with excellent elastic recovery. Printed objects include a 3D aortic arch and branched carotid artery rendered from anonymized patient CT scans and microfluidic devices with patent 3D corkscrew channels. Caffeine-catalysis affords various percentages of alcohol chain end that control the photopolymer's degradation rate. The material demonstrates good biocompatibility in vitro and in a subcutaneous implantation model. The elasticity, biocompatibility, affordability, sustainability, and versatility of this new photopolymer platform will open up new opportunities for sustainable 3D printing materials.