Crystallization Induced Stress Decay in Crosslinked Shape-memory Networks

Polymer crystallization within crosslinked elastomeric networks can reduce mechanical tension, forming the basis for semicrystalline shape-memory polymers. However crystallization is path-dependent and is sensitive to both mechanical strain and thermal undercooling. By utilizing in situ wide-angle x-ray scattering, we investigated the coupling between isothermal crystallization and stress decay under fixed strains ranging from 25 to 100%. Our results showed that significant stress reduction can occur at only a few percent crystallinity (<0.05). Depending on the annealing process, the dependency of stress decay could either match or surpass the dependency predicted by Flory in crosslinked natural rubber. This study contributes to understanding the interrelationship between crystallization, stress reduction, and material stiffening to support further development of semicrystalline shape-memory networks.