Relaxation transitions in poly(vinylidene fluoride)

Kuleshov, I.V.; Бартенев, Г. М.

doi:10.1002/actp.1988.010390605

Cited by 2 publications

(1 citation statement)

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“…1,2,4 And therefore in the regions of spontaneous polarization order-disorder transitions are observed. 20,21,25,30 Large number of dielectric measurements illustrate that the a c -transition is clearly observed in PVDF crystallized in nonpolar phase, but practically disappears in this polymer in polar b-modification. 22 It is known that for the latter the conformation of plain zigzag is typical, with dipolar moment perpendicular to the macromolecular axis, while the chains in a-phase have TGTG À conformation, which have nonzero component of the dipole moment m jj directed along the chain axis.…”

Section: Introductionmentioning

confidence: 96%

Dielectric relaxation in vinylidene fluoride–hexafluoropropylene copolymers

Kochervinskiĭ

Malyshkina

Markin

et al. 2007

J of Applied Polymer Sci

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The molecular mobility in copolymers of vinylidene fluoride-hexafluoropropylene VDF/HFP of 93/7 and 86/14 ratios has been investigated by means of broadband dielectric relaxation spectroscopy (10 À1 -10 7 Hz), differential scanning calorimetry DSC (À100 to 1508C), and of wide angle X-ray diffraction WAXS. Four relaxation processes and one ferroelectric-paraelectric phase transition have been detected. The process of the local mobility b-(at temperatures below glass transition point) is not affected by chemical composition of the copolymer and the formed structure. Parameters of segmental mobility in the region of glass transition (a a -relaxation) depend on the ratio of comonomer with lower kinetic flexibility. a c -relaxation is clearly observed only in VDF/HFP 93/7 copolymer, which is characterized by a higher crystallinity and a higher perfection of crystals of a-(a p -) phase. Diffuse order-disorder relaxor type ferroelectric transition connected with the destruction of the domains in low-perfect ferroelectric phase in the amorphous regions has been detected for both copolymers. An intensive relaxation process (a-process) was observed for both copolymers in high-temperature region. DSC data shows that it falls on the broad temperature region of aphase crystals melting. It is considered to be connected with the space charge relaxation.

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