Crystal structure of polychlorotrifluoroethylene

The crystal structure of polychlorotrifluoroethylene has been studied. The pseudohexagonal lattice parameters are a = 6.438, c = 41.5 Å. The polymer chain is found to be helical with on the average 16.8 monomer units in one turn of the helix (equal to c). The skeletal angles on the CF₂ and CFCI atoms are found to differ by 5 to 7 degrees. The polymer chain is found to accommodate these alternating angles by twisting around the axis of the helix. The result of the x-ray diffraction study agrees best with the assumption that the polymer is atactic with random position of the chlorine substituent. This randomness affects the microstructure of the polymer chain to such an extent that the diffraction effects are those of a system of continuous helices.