Metal-free, scalable synthesis of degradable polyester resins for high-resolution DLP 3D printing via organoboron-catalyzed ROCOP

Abstract

The widespread adoption of digital light processing (DLP) 3D printing is severely constrained by the lack of sustainable photopolymer resins; conventional acrylate-based systems suffer from toxicity, non-degradability, and poor biocompatibility. Polyesters derived from ring-opening copolymerization (ROCOP) of cyclic anhydrides and epoxides have emerged as eco-friendly alternatives, but their synthesis relies on metal-based catalysts. Herein, we address these challenges by reporting a metal-free, scalable, and atom-efficient route to a degradable polyester oligomer, poly(allyl glycidyl ether phthalate) (PAGEP), via bifunctional organoboron-catalyzed ROCOP of phthalic anhydride (PA) and allyl glycidyl ether (AGE). The organoboron catalyst exhibits exceptional activity at an ultra-low loading of 100 ppm, enabling facile kilogram-scale synthesis in an academic laboratory. Stoichiometric control over the degree of polymerization yields low M_n PAGEP with inherently low viscosity, ensuring compatibility with DLP 3D printing. Structural characterization via ¹H NMR, diffusion-ordered spectroscopy (DOSY) NMR, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) confirms a well-defined alternating copolymer structure. By optimizing the resin formulation and single-layer exposure time, we fabricate high-resolution 3D-printed parts with elastomeric properties via thiol–ene photopolymerization of the resins with a tetrathiol crosslinker (PETMP) (ultimate tensile strength: 1.5–2.4 MPa; elongation at break: 24–32%). Critically, PAGEP-based printed parts undergo complete degradation within 10 days under accelerated hydrolysis conditions (0.1 N NaOH), eliminating environmental accumulation concerns.