Deciphering Internal Stress Dynamics: Generation and Relaxation Mechanisms in Photocuring

Cross-linking during photocuring restricts chain and segmental mobility, causing internal stress accumulation that compromises interfacial strength and dimensional stability. In this study, rheological methods are employed to track the evolution of stress and volumetric change in acrylates throughout the entire curing process─from the liquid-to-solid transition (gelation), through vitrification, to reaction saturation. Time–intensity–transformation (TIT) and time–temperature–transformation (TTT) diagrams are constructed by correlating curing parameters (light intensity (1.34–5.70 mW/cm2) and curing temperature (30–55 °C)) with stress profiles. By simultaneously increasing reaction temperature and decreasing light intensity, we obtain sets of samples with matched gelation rates. Nevertheless, their mechanical performance varies systematically due to polymerization heterogeneity governed by the relative rates of chain diffusion and chemical reaction. The findings not only deepen the mechanistic understanding of photopolymerization but also provide a strategy for tailoring mechanical performance through optimized curing protocols.