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 green-house 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 investi-gated by J.P. Joule in natural rubber. Herein, we demonstrate that polymer elastomers with molecular chains near molecular -struc-ture-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 polysty-rene-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.