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 that introduce toxic residues and increase production costs. 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 using commercially available monomers. Stoichiometric control over polymerization yields PAGEP with inherently low viscosity (19.9 Pa•s for neat polymer), ensuring compatibility with DLP 3D printing (0.37 Pa•s with 20 wt% ethyl acetate as diluent). 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 parts with elastomeric properties (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.2