Beyond Disulfide Content: Network Architecture and Chain Mobility as Key Determinants of Self-Healing Efficiency in Photocured Polyurethane Acrylate Networks

Disulfide-containing dynamic covalent polymer networks offer a promising molecular strategy for imparting thermally activated self-healing capability to permanently crosslinked photopolymer systems; however, the relative contributions of disulfide bond density, crosslinking architecture, and segmental chain mobility to mechanical recovery remain insufficiently understood. In this study, a series of photocurable disulfide-containing polyurethane acrylate (PUA) networks was designed by systematically varying the content of disulfide-containing segments and incorporating triethylene glycol dimethacrylate (TEGDMA) as a difunctional crosslinker to decouple the effects of dynamic bond exchange, network rigidity, and chain mobility on self-healing performance. Raman spectroscopy confirmed the incorporation of disulfide bonds in proportions consistent with the synthesis molar ratios, and all photocured networks achieved degrees of conversion ranging from 77.0% to 85.1%. DSC analysis revealed that TEGDMA incorporation significantly increased the glass transition temperature, reflecting enhanced network rigidity through increased crosslinking density, at the cost of reduced elongation at break. After surface damage, disulfide-containing formulations exhibited substantially higher tensile-strength recovery than non-disulfide controls, confirming the critical role of dynamic S–S bond exchange in mechanical recovery. Notably, healing efficiency was not governed solely by disulfide content: treatment temperature, treatment duration, crosslinking density, and chain mobility collectively determined the extent of recovery. Among the investigated networks, one printable formulation achieved a healing efficiency of 92% under mild conditions (40°C, 7 days), demonstrating the feasibility of low-temperature self-repair. These results establish that effective self-healing in photocured PUA networks requires coordinated tuning of dynamic bond exchange, network mobility, and crosslinking density, providing molecular design guidelines for developing repairable and mechanically robust photopolymer materials.