High-entropy polymer produces a giant electrocaloric effect at low fields

Area of Science:

• Materials Science
• Thermodynamics
• Polymer Chemistry

Background:

• Decades of research on electrocaloric (EC) effect materials and multilayer chips have achieved the minimum temperature change (5 K) for caloric heat pumps.
• Current EC materials require high electric fields, leading to degradation and fatigue, limiting practical applications.

Purpose of the Study:

• To report a new class of EC polymer with enhanced performance.
• To investigate the structural modifications responsible for improved EC properties.
• To assess the material's suitability for practical caloric heat pump applications.

Main Methods:

• Synthesized a modified poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer by converting chlorofluoroethylene groups into covalent double bonds.
• Characterized the electrocaloric properties, including entropy and temperature change, under varying electric fields.
• Evaluated material performance and stability over one million cycles.

Main Results:

• The novel EC polymer demonstrated an EC entropy change of 37.5 J kg⁻¹ K⁻¹ and a temperature change of 7.5 K at 50 MV m⁻¹.
• Achieved a 275% enhancement in temperature change compared to state-of-the-art EC polymers under the same field strength.
• The structural modification increased polar entities and polar-nonpolar interfacial areas, leading to a high-entropy state with low switching energy barriers.

Conclusions:

• The developed EC polymer exhibits superior performance and stability under moderate electric fields.
• The strategy of incorporating covalent double bonds offers a promising route for designing advanced EC materials.
• This material shows significant potential for practical caloric heat pump applications due to its enhanced efficiency and durability.