Enhanced Electrocaloric Response of Vinylidene Fluoride-Based Polymers via One-Step Molecular Engineering

Electrocaloric refrigeration is one of the most promising environmentally-friendly technologies to replace current cooling platforms-if a notable electrocaloric effect (ECE) is realized around room temperature where the highest need is. Here, a straight-forward, one-pot chemical modification of P(VDF-ter-TrFE-ter-CTFE) is reported through the controlled introduction of small fractions of double bonds within the backbone that, very uniquely, decreases the lamellar crystalline thickness while, simultaneously, enlarging the crystalline coherence along the a-b plane. This increases the polarizability and polarization without affecting the degree of crystallinity or amending the crystal unit cell-undesirable effects observed with other approaches. Specifically, the permittivity increases by >35%, from 52 to 71 at 1 kHz, and ECE improves by >60% at moderate electric fields. At 40 degrees C, an adiabatic temperature change >2 K is realized at 60 MV m(-1)(>5.5 K at 192 MV m(-1)), compared to approximate to 1.3 K for pristine P(VDF-ter-TrFE-ter-CTFE), highlighting the promise of a simple, versatile approach that allows direct film deposition without requiring any post-treatment such as mechanical stretching or high-temperature annealing for achieving the desired performance.

Automated summary

The study presents a method of modifying P(VDF-ter-TrFE-ter-CTFE) by introducing small fractions of double bonds in the molecular backbone, which significantly enhances the electrocaloric effect without the need for post-treatments such as mechanical stretching or high-temperature annealing.