Zhu, Y.; Wu, H.; Martin, A.; Beck, P.; Allahyarov, E.; Wongwirat, T.; Rui, G.; Zhu, Y.; Hawthorne, D.; Fan, J.; Wu, J.; Zhang, S.; Zhu, L.; Kaur, S.; Pei, Q. Operando Investigation of the Molecular Origins of Dipole Switching in P(VDF-TrFE-CFE) Terpolymer for Large Adiabatic Temperature Change. Adv Funct Mater 2024, 2314705, 1–12. https://doi.org/10.1002/adfm.202314705.
Relaxor ferroelectric polymers exhibiting a giant electrocaloric effect (ECE) can potentially be used to create next-generation solid-state coolers. Under an electric field, poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer goes through a large dipolar entropy change producing a high adiabatic temperature change (𝚫TECE). This work resolves the molecular origins of the large entropy change behind the electric field-induced dipole switching. A Fourier transform infrared spectroscopy equipped with a high voltage source is used to operandoly observe the characteristic molecular vibrational modes. A short-range trans (T) conformation of the CF2-CH2 dyads interrupted by a gauche (G) conformation, e.g., TTTG in the terpolymer chain, undergoes a dynamic transformation that leads to a corresponding 𝚫TECE whenever an electric field is applied. The molecular dynamics simulation also proves that the energy barrier that the transformation from TTTGs into a long T sequence overcomes is smaller than that for all other conformations. A mixed solvent system is used to obtain T3G-enriched terpolymer films exhibiting a 4.02 K 𝚫TECE at 60 MV m−1 and these films are employed to manufacture a 2-layer-cascaded cooling device that achieves a 6.7 K temperature lift, the highest reported value for a 2-layer cascaded device made of fluoropolymers.