posted on 2023-01-04, 20:11authored byXin Chen, Hancheng Qin, Wenyi Zhu, Bing Zhang, Wenchang Lu, J. Bernholc, Q. M. Zhang
Polymers that generate large shape changes under electric
stimulation
are of great interest for many applications. Recently, it was shown
that converting a small amount of chlorofluoroethylene (CFE) in relaxor
ferroelectric poly(vinylidene fluoride–trifluoroethylene–CFE)
(PVDF-TrFE-CFE) terpolymer into fluorinated alkyne (FA) creates P(VDF-TrFE-CFE-FA)
tetrapolymers with giant electromechanical (EM) response at ultralow
electric fields (<50 MV/m). We investigate the microscopic origin
of this effect and show that converting the bulky CFE into small-size
FA defects dramatically weakens the relaxor behavior. Importantly,
P(VDF-TrFE-CFE-FA) tetrapolymers with near 2 mol % FA exhibit a diffused
critical endpoint transition region at which the energy barriers for
switching from nonpolar to polar molecular conformations become small.
Consequently, a small change of the electric field induces a large
electroactuation, which can enable novel applications. This work opens
up a totally new approach to designing ferroelectric polymers that
generate large responses at ultralow electric fields.