ELECTRON-DIFFRACTION INVESTIGATION OF A HIGH-TEMPERATURE FORM OF POLY(VINYLIDENE FLUORIDE)

Thin films of poly(vinylidene fluoride), crystallized from the melt at temperatures above 160 °C, were examined by electron microscopy and diffraction. Immature spherulites of a high-melting form were found to be composed of collections of flat platelets with remarkably regular crystallographic growth facets. Electron diffraction patterns from these are not consistent with any of the commonly accepted unit cells for this polymer but are instead in agreement with a new unit cell that has recently been found in solution-grown samples and appears to be the correct one for γ-PVF2. When tilted in the electron microscope, these melt-crystallized samples yielded diffraction patterns indicating that the molecular chains are not normal to the broad lamellar surfaces but are instead rotated about the b axis of the unit cell to an angle of 28.5° from the lamellar normal. © 1979, American Chemical Society. All rights reserved.