Polymer elastomer near plastic-to-rubber critical transition produces enhanced elastocaloric effects

Solid-state cooling technology based on elastocaloric effects has shown potential advantages over traditional vapor-compression cooling systems owing to its high energy efficiency and zero greenhouse gas emissions. However, a lack of strategies for improving the elastocaloric activity of polymers remains the main obstacle to their commercialization since the elastocaloric effect was first investigated by J.P. Joule in natural rubber. Herein, we demonstrate that polymer elastomers with molecular chains near molecular-structure-induced plastic-rubber critical transitions exhibit superior elastocaloric activity through reversible conformational changes. As the content of ethyl side groups in the soft block of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene decreases from 33 to 8 mol %, the adiabatic temperature change increases from −4.3 to −16.3 K, and the isothermal entropy change increases from 38.5 to 173.3 J kg⁻¹ K⁻¹, which thus shows the highest polymer elastocaloric activity near room temperature. This strategy could promote the commercialization of elastocaloric polymers in solid-state cooling applications.