Simultaneous Wide-Angle X-Ray Diffraction and Differential Scanning Calorimetry Analysis of the Melting and Recrystallization Behavior of Polyethylene and Isotactic Polypropylene Containing Cyclopentane Units in the Main Chain

The melting and crystallization behavior of polyethylene and isotactic polypropylene containing 1,2- or 1,3-disubstituted cyclopentane units in the main chain has been studied with simultaneous wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry. For the ethylene-based copolymers, the position of a reflection peak in the WAXD patterns shifts to a low angle with the increasing acquired temperature. The temperature dependence on the axial length of the crystal lattice is more marked in the copolymers forming orthorhombic crystals (containing 1,2-cyclopentane or 5.6 mol % 1,3-cyclopentane units) than in those forming hexagonal crystals (containing 8.1 mol % 1,3-cyclopentane units). For the isotactic propylene-based copolymers, the position of the reflection peaks in the WAXD patterns is independent of the acquired temperature. The proportion of the γ form in the copolymer containing the 1,2-cyclopentane units is higher than that in the copolymers containing the 1,3-cyclopentane units.