Abstract
In the search for fluorinated polymers with newelectroactive properties, the radical polymerization of vinylidenefluoride (VDF), trifluoroethylene (TrFE), and trans-1,3,3,3-tetrafluoropropene (1234ze) was achieved. The crystallineorganization and the electroactive properties of semicrystallinepoly(VDF-ter-TrFE-ter-1234ze) terpolymer films with 1234zemolar contents ranging from 0 to 6%, obtained by solventcasting,were investigated using a combination of structural,dielectric, and electromechanical techniques. For 0 mol %1234ze, poly(VDF-co-TrFE) copolymers exhibited a Curietransition from the ferroelectric (FE) phase to the paraelectric (PE) phase at the Curie temperature (TC ∼ 95 °C). DSC,dielectric spectroscopy, and FTIR experiments revealed the preservation of this Curie transition (TC ∼ 75 °C) while increasingthe termonomer content. WAXS measurements confirmed the persistence of the FE phase as the main phase at roomtemperature but also showed the appearance of a secondary ZFE phase (expanded FE phase incorporating 1234ze units) in lowerproportion. The WAXS crystallinity was halved (42 to 23%) from 0 to 6 mol % 1234ze terpolymer annealed films. Furthermore,SAXS and WAXS experiments highlighted a decrease of the crystalline lamellae thickness and a significant modification of theelectronic density distribution upon increase of 1234ze units. A new model for this particular arrangement of crystalline lamellaewas thus proposed with the location of the ZFE phase at the interface between the FE crystalline lamellae and the amorphousphase. Finally, reduced remnant polarization (Pr ∼ 15 mC/m2) and transverse piezoelectric coefficient (d33 ∼ −5 pC/N),compared to those of the reference poly(VDF-co-TrFE) copolymer (Pr ∼ 50 mC/m2 and d33 ∼ −20 pC/N), were mainlyassigned to the decrease of the FE phase content in terpolymer poled films.