An Elastomer with Giant Strain-Induced Crystallization

Strain-induced crystallization prevalently strengthens, toughens, and enables an elastocaloric effect in elastomers. However, the crystallinity induced by mechanical stretching in common elastomers (e.g., natural rubber) is typically below 20%, and the stretchability plateaus due to trapped entanglements, impeding performance for advanced applications. We present a new class of elastomers formed by end-linking then deswelling star polymers with a low fraction of defects and no trapped entanglements, which achieve strain-induced crystallinity of up to 50%. The deswollen end-linked star elastomer (DELSE) reaches an ultra-high stretchability of 12.4-33.3, scaling beyond the saturated limit of common elastomers. The DELSE also exhibits a high fracture energy of 4.2-4.5 kJ/m/m while maintaining low hysteresis. The heightened strain-induced crystallization and stretchability synergistically promote a high elastocaloric effect with an adiabatic temperature change of 9.3 °C at 54 °C, compared with 3.5 °C at 54 °C in natural rubber.