Ordered Arrangement of Bent and Faceted Single Crystals of Poly(vinylidene Fluoride)

Bent and faceted single crystals of poly(vinylidene fluoride) (PVDF) were prepared by isothermal crystallization in its blends with poly(butylene succinate) (PBS). After removing PBS by CHCl3 washing, the remaining PVDF crystals were examined by optical, atomic force, and transmission electron microscopies and Fourier transform infrared spectroscopy. PVDF single crystals are attributed to alpha-phase and can reach hundreds of microns with two or more bent branches. The C- and X-shaped crystals are composed of bent basal lamellae, seen flat-on, with a great number of overgrowths. The overgrowths are lozenge-shaped, small-sized single crystals, and most of them grow along the C curves of either C-shaped or X-shaped crystals, keeping the same growth direction with the basal one. Consequently, the electron diffraction patterns taken everywhere of the whole crystal exhibit always a single crystal feature but change constantly with b-axis. These may be attributed to the unbalanced growth of four (110) faces and an inhomogeneous surface order or arrangement of loops and cilia. The lozenge-shaped, large-sized monolayer crystal can be observed upon decreasing the film thickness but without overgrowth, and its shape changes with crystallization temperature. These results can help to understand the surface structure of lamellae and its proliferation process profoundly.

Automated summary

Bent and faceted single crystals of PVDF were prepared by isothermal crystallization in its blends with PBS. The PVDF crystals can reach hundreds of microns with bent branches and are composed of bent basal lamellae with overgrowths. The electron diffraction patterns exhibit a single crystal feature but change constantly with b-axis, which may be attributed to the unbalanced growth of four (110) faces and an inhomogeneous surface order or arrangement.