The structure of oriented compositions based on simplest polyolefins obtained by in situ polymerization on a new catalytic system

Temperature-induced evolution of the structure of oriented films of three P E-PP blend compositions was studied by X-ray diffraction and DSC. The blend s were obtained by in situ polymerization using a common catalytic system c omprising a binuclear metal complex catalyst supported on a solid carrier. On heating, the isotropic samples exhibit two "ordinary" phase transitions reflecting sequential melting of the two blend components. The uniaxially o riented films of similar composition, deformed to various degrees, exhibit a more complicated pattern of phase transitions. In particular, the melting of the PE component is a two-stage process; with the transition from an or thorhombic phase to pseudohexagonal mesophase in the first stage and the me lting of the mesophase and isotropization of the material, in the second st age. This behavior is related to the presence of two fractions of dispersed component in the PE phase of the oriented blend. One of these fractions ex hibits crystallization with folded chains, while the other fraction crystal lizes with unfolded macromolecules.