Origins of Electrostriction in Poly(vinylidene fluoride)-Based Ferroelectric Polymers

• Published in: Macromolecules 2020-12, Vol.53 (24), p.10942-10954
• Main Authors: Wongwirat, Thumawadee, Zhu, Zhiwen, Rui, Guanchun, Li, Ruipeng, Laoratanakul, Pitak, He, Hezhi, Manuspiya, Hathaikarn, Zhu, Lei
• Format: Article
• Language: English
• Subjects: MATERIALS SCIENCE
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.0c02083

Although electrostriction is ubiquitous for dielectric polymers, giant electrostriction has not been observed until relaxor ferroelectric (RFE) poly­(vinylidene fluoride) (PVDF)-based polymers are achieved. However, the exact origin for giant electrostriction in these polymers has not been fully understood. By studying the electrostriction in the uniaxially stretched films of a ferroelectric poly­(VDF-co-trifluoroethylene) [P­(VDF-TrFE)] random copolymer and an RFE poly­(VDF-co-TrFE-co-chlorotrifluoroethylene) [P­(VDF-TrFE-CTFE)] random terpolymer in this work, we confirmed that ferroelectric switching with large hysteresis, such as in the case of P­(VDF-TrFE), was not genuine electrostriction. By decreasing large ferroelectric domains to the nanometer scale (i.e., 2–3 nm), such as in the case of the P­(VDF-TrFE-CTFE) terpolymer, electrostriction with low hysteresis could be achieved. Two origins of the large electrostriction in these polymers were identified. The first was the mechano-electrostriction due to the poling field-induced conformation transformation of oriented polymer chains. The second was the electric repulsion of electrically aligned nanodomains. These effects could occur in both crystals and the oriented amorphous fraction, which links between the nanocrystals and the isotropic amorphous fraction. When the poling field was relatively low (e.g.,