Influence of Cross-Link Density on the Photopolymerization of Degradable Methacrylated Sugar Networks via Thiol-ene Chemistry

A series of biobased poly(ester-thioether) thermosets was developed from sugar-derived methacrylate monomers and characterized for their structure–property relationships. Xylose, glucose, and sucrose were functionalized via a one-step esterification with methacrylic anhydride to yield tetra-, penta-, and octa-methacrylated monomers, respectively. Thiol-ene photopolymerization with five dithiol cross-linkers produced 15 distinct thermoset networks. Fourier transform infrared spectroscopy (FTIR) confirmed successful cross-linking through the disappearance of the thiol peak at ∼2560 cm–1. Thermal analysis revealed that temperatures at 5% weight loss (T5%) and midpoint degradation temperatures (Tmid) increased with cross-link density (νc), with sucrose-based networks exhibiting the highest thermal stability. Dynamic mechanical analysis (DMA) showed glass transition temperatures (Tg) between 73 and 96 °C and an inverse relationship between molecular weight between cross-links (Mc) and the storage modulus (E′), indicating that network rigidity is governed by both νc and monomer architecture. Alkaline degradation studies confirmed ester hydrolysis by mass loss over time, with degradation rates influenced by network structure. Soil degradation exhibited minimal yet detectable environmental degradation, suggesting a balance between durability and eco-responsiveness. These results highlight the potential of sugar-derived multifunctional monomers for designing degradable, high-performance thermosets for stereolithography (SLA) and digital-light processing (DLP) 3D-printing resins, transparent coatings, and recyclable adhesive systems.