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

Abstract

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 CHCl 3 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 α-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.

Proliferation and Arrangement of Poly(vinylidene fluoride) Oval γ Single Crystals Grown in Its Poly(1,4-butylene adipate) Blends

“…Figure a shows an OM image of PVDF crystals grown in a PVDF/PBA blend film isothermally at 150 °C for 18 h after removing the PBA component. We can find some lozenge-shaped crystals, which are α-PVDF single crystals as identified in our previous study and also reported in some other references. ,,− In addition, several ellipse-shaped crystals, as marked by the dotted circles, are also visible. Figure b presents an AFM height image of an ellipse-shaped single crystal shown in Figure a.…”

“…Because the PBS is miscible with PVDF in amorphous state and has rather lower melting temperature than PVDF, it acts as a diluent during crystallization of PVDF at high temperatures and can be easily removed by selective solvent from the prepared sample. 40 As a result, abundant faceted α-PVDF single crystals have effectively been obtained, and their ordered arrangement has been investigated. In the present study, a little amount of PVDF (weight ratio 5 wt %) was blended with another low-melting-point polyester, i.e., poly-(1,4-butylene adipate) (PBA) with a low melting temperature of ca.…”

“…In our previous work, the isothermal crystallization of PVDF in its blends with poly­(butylene succinate) (PBS) has been studied. Because the PBS is miscible with PVDF in amorphous state and has rather lower melting temperature than PVDF, it acts as a diluent during crystallization of PVDF at high temperatures and can be easily removed by selective solvent from the prepared sample . As a result, abundant faceted α-PVDF single crystals have effectively been obtained, and their ordered arrangement has been investigated.…”

Chirality Hierarchical Transfer in Homochiral Polymer Crystallization Under High-pressure CO2

“…The growth direction of the upper layer of crystals is dominated by the basal layer, and the growth direction of the entire dendrite is also dominated by the basal layer. The research of Shen et al (31) also supports this viewpoint.…”

“…The cilia will cause abnormal surface density, resulting in imbalanced stress. Surface stress induces chain tilt, which in turn leads to an imbalanced growth rate on the side of the lamellar crystal (31,33), nally resulting in the formation of right-hand helical dendrites.…”