STRUCTURE OF THE AMORPHOUS PHASE IN CRYSTALLIZABLE POLYMERS - POLY(ETHYLENE-TEREPHTHALATE)

Evidence for spatial correlations of the polymer chains in the amorphous phase of crystallizable polymers is presented by using the X-ray diffraction patterns of poly(ethylene terephthalate) resins, films, and fibers. The necessity of resolving the amorphous halo between 5-degrees and 35-degrees 2-theta (Cu K-alpha) into at least two peaks (s = 0.20 and 0.26 angstrom-1) suggests that there can be more than one average interchain distance in the amorphous phase. The two distances might arise from the rotational correlations of the aromatic groups on adjacent chains. The relative intensity of the two amorphous peaks was found to depend on the thickness in quich-quenched films, on the temperature in variable-temperature scans of crystalline powders, and on the azimuthal angle in oriented fibers. These variations in the intensities of the two peaks are attributed to changes in the short-range ordering of the amorphous chain segments. Further, the nonzero base line in the plot of the variations in the scattered intensity with azimuthal angle suggests that the amorphous scattering can be conceptually separated into isotropic and anisotropic components.