An Elastocaloric Polymer with Ultra-High Solid-State Cooling via Defect Engineering

Area of Science:

• Materials Science
• Polymer Science
• Thermodynamics

Background:

• Elastocaloric polymers offer a sustainable alternative to traditional refrigeration by utilizing phase transformations.
• Engineering polymer networks can enhance elastocaloric performance, but the impact of topological defects is largely unknown.
• Topological defects are common in polymers and may influence their elastocaloric properties.

Purpose of the Study:

• To investigate the role of topological defects in elastocaloric polymers.
• To develop a defect-engineering strategy for enhancing elastocaloric cooling in end-linked star polymers (ELSPs).
• To understand the relationship between defect concentration and adiabatic temperature change.

Main Methods:

• Synthesized end-linked star polymers (ELSPs) with varying concentrations of dangling-chain defects.
• Characterized the elastocaloric properties, including adiabatic temperature change, of the synthesized polymers.
• Analyzed the influence of defects on strain-induced crystallization (SIC) and temperature-induced crystallization (TIC).

Main Results:

• Achieved an adiabatic temperature change of up to 8.14 ± 1.76 °C at ambient temperatures above 65 °C.
• Demonstrated a 39% enhancement in elastocaloric performance compared to defect-free ELSPs.
• Identified competing effects of dangling-chain defects on SIC and TIC, which synergistically regulate the adiabatic temperature change.
• Observed that increasing defects monotonically lowers high-temperature mechanical performance (suppressed SIC) but non-monotonically impacts low-temperature performance (competing SIC and enhanced TIC).

Conclusions:

• Defect engineering in ELSPs is a viable strategy to significantly boost solid-state cooling performance.
• The interplay between SIC and TIC, modulated by dangling-chain defects, is crucial for optimizing elastocaloric effects.
• This work provides fundamental insights into defect-property relationships in elastocaloric polymers, paving the way for advanced cooling materials.