The mid-infrared(MIR)spectroscopy(including one dimensional MIR spectroscopy,second-order derivative MIR spectroscopy,fourth-order derivative MIR spectroscopy,and deconvolution MIR spectroscopy)was used to study the γ-crystalline structure of polyvinylidene fluoride(PVDF),respectively.It was found that at 303 K,the infrared absorption frequency(v(γ-crystalline structure-deconvolution))of the γ-crystalline structure of PVDF was 1 235.75 cm-1.The effect of temperature variation on the the γ-crystalline structure of PVDF was further investigated by using the deconvolution temperature-dependent MIR spectroscopy.It was found that the absorption intensity of PVDF(γ-crystalline structure-deconvolution)increased with the increase of the determined temperature at 303～523 K.The increase of temperature could promote the transformation of some α-crystalline and β-crystalline forms of PVDF intoγ-crystalline forms.The thermal denaturation of γ-crystalline structure in PVDF was further investigated by using the two dimensional MIR spectroscopy.At 303～523 K,the sensitive degree of the absorption peak of γ-crystalline structure in PVDF to the variation of temperature and the changing speed information were somewhat different.Before the phase transition,the information on the variation speed of the absorption peak of γ-crystalline structure in PVDF was as follows:the absorption peak at 1 237 cm-1(v(γ-crystalline structure-2-two dimensional-before the phase transition))changed earlier than the absorption peak at 1 241 cm-1(v(γ-crystalline structure-1-two dimensional-before the phase transition));during the phase transition process,the variation speed of the absorption peak of y-crystalline structure in PVDF was in the following order:the absorption peak at 1 244 cm-1(v(γ-crystalline structure-1-two dimensional-during the phase transition process)),absorption peak at 1 239 cm-1(v(γ-crystalline structure-2-two dimensional-during the phase transition process)),absorption peak at 1 236 cm-1(v(γ-crystalline structure-3-two dimensional-during the phase transition process)),and absorption peak at 1 234 cm-1(v(γ-crystalline structure-4-two dimensional-during the phase transition process)).
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