Microphase Separation Regulation of Polyurethane for Achieving a Significant Elastocaloric Effect

The elastocaloric effect (eCE) enables solid-state cooling through reversible, stress-induced thermal changes, yet its practical implementation remains limited by insufficient control over microphase separation in elastomeric materials. Here, we report a solubility-parameter-guided solvent-processing strategy that enables precise, scalable regulation of microphase separation in segmented polyurethane (PU) elastomers without chemical modification. A mixed N,N-dimethylacetamide/1,4-dioxane (DMAc/DIOX) solvent system with a continuously tunable solubility parameter (δ = 18.02–21.40) was employed to enable selective dissolution of hard and soft segments during solution casting, inducing a controlled dissolution–precipitation process. When δ approaches the hard-segment value, PU exhibits the most distinct microphase separation, characterized by a high hydrogen-bond index (75.3%), a reduced soft-segment glass-transition temperature (224 K), and well-defined hard domains, enabling efficient strain-induced ordering. This optimized microstructure yields a large adiabatic temperature change of 19.1 K under low-stress stretch–recovery conditions. These results demonstrate that solubility-parameter-driven solvent design offers an effective, scalable, and general route to optimize microphase separation. This work provides a promising pathway for sustainable thermal management technologies in segmented polymer systems.