Chain Length Effects on Crystal Formation in Vinylidene Fluoride Oligomers

Abstract

Crystal modifications in vinylidene fluoride (VDF) oligomers, such as α, β, and γ forms, were studied as a function of the molecular chain length. VDF oligomers were prepared by a telomerization method and the oligomers were fractionated by vacuum vapor deposition. The fractionated oligomers were crystallized from the melt. The crystal forms in VDF oligomers were characterized by IR, X-ray, and DSC methods. The β form was found in the degree of polymerization (N) less than 10, the α form consisted of N ranging from 10 to 16 and the γ form was observed in N above 16. The effect of molecular chain length on the crystal forms in VDF oligomers could be associated with change in the conformational energy accompanying the steric hindrance along the molecular chain for the β form and differences in the crystallization behavior from the melt for the α and γ forms.