Submillimeter and far infrared spectroscopic analysis of a ferroelectric Poly (vinylidene fluoride) copolymer

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Abstract
Far infrared spectra of Poly(vinylidene fluoride hexafluoropropylene copolymer: P(VDF-HFP), has been studied between 20 and 250 cm−1. After correction of the interference phenomenon affecting the measurements, we have observed the evolution of the transmission coefficients as a function of the HFP molar content with and without low electrical polarisation. If HFP presence seems principaly to increase the amorphous part of the copolymers, it would also favourise the presence of T3GT3G' defects. Piezoelectric activity obtained on this copolymer, under low electrical stresses, confirms the presence of a ferroelectric structure linked to chain sequences of PVDF polar form 11 or αp and also to T3GT3G' defects. A millimeter infrared absorption band theoretically predicted at 30 cm−1, for translational movement along crystalline c axis of PVDF α form, can be detected. Such a mode, theoretically forbidden in infrared for an ideal chain, can be activated by the presence of defects.