The phase structure and orientation effects of poly (vinylidene fluoride) (PVDF) films under uniaxial tension were characterized by 19F and 1H NMR. Sample films were prepared by solution-casting after which they were stretched at different temperatures (160 oC, 120 oC, 100 oC and 80 oC). This allowed for the study of induced order due to stretching and the characterization of phase content with preparation temperature. The studied films were stretched to 550%, 400%, and 300% of their original length. 1H and 19F solid-state static NMR spectra were gathered for various orientations of the stretch direction relative to the pulse field and external magnetic field. The 1H line shape is subdivided into amorphous (mobile) and crystalline components. The crystalline component is a Pake doublet and shows a strong orientation dependence, indicative of the order induced in the film upon stretching. The results are particularly notable for the beta-phase PVDF, as observed in the 80oC and 100oC stretched films. The amorphous component displays a mild orientation dependence in all stretched films. A similar interpretation can be made for the 19F results, although the spectra are characterized by large chemical shift anisotropies. Correlations between the extent of stretching and distributions (i.e., H-H internuclear vector orientations and 19F CSA components from the line shape analyses) provides a picture of the enhanced ordering of the crystalline PVDF phases.

Probing phase structure and orientation effects of uniaxially stretched poly (vinylidene fluoride) films by solid-state NMR

256th National Meeting (2018)

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