Thermal induced anisotropic deformation of DCPD gels during frontal polymerization

As an emerging low-energy-consumption and rapid-processing technique, frontal polymerization (FP) has garnered increasing attention due to its significant potential in free-standing three-dimensional printing, advanced composite manufacturing etc. However, effects from thermal expansion, chemical shrinkage, and nonuniform reaction propagation during the FP process inevitably generate gradient deformations at the FP front, adversely affecting the mechanical properties of the final processed components. To elucidate the intrinsic deformation mechanisms of polymer materials during FP and optimize their mechanical performance after polymerization, we employ a representative dicyclopentadiene (DCPD) gel system for investigation. In this study, simultaneous temperature and strain measurement revealed anisotropic deformation patterns of DCPD gels during FP. Meanwhile, experimental and numerical studies investigated the strain evolution of DCPD gels during both single and multi-point initiation of FP, revealing that the maximum compressive strain in uncured regions gradually decreased with increasing pre-curing degree but increased with rising width. Finally, mechanical characterization results show that, as the pre-curing degree increases, both compressive and tensile performances of polydicyclopentadiene are progressively enhanced, with yield strengths under tension and compression at 77 K significantly exceeding those at room temperature. These findings provide an experimental and theoretical foundation for high-performance material fabrication based on FP of gel-state systems.