SAXS DETERMINATION OF THE AMORPHOUS SURFACE-LAYER THICKNESS OF POLYMER SINGLE-CRYSTALS

In the reported study, polyethylene single crystals were grown from 0. 1% solutions in xylene at 80 and 87 degree C. Oriented mats were made from each preparation and the small-angle x-ray scattering (SAXS) profiles obtained. Following treatment of the raw data for main-beam position and width, background scatter, and the Lorentz factor, five Bragg reflections were resolved. A one-dimensional lattice was used as a model for the oriented mats of single crystals. This model contains three parameters. An additionl parameter G//x was also introduced to demonstrate the general effect of a broadening factor on the model. The effect of each parameter on the calculated diffraction pattern was examined. From this examination it was found that by assuming that the broadening functions are zero, one can determine directly from the number of observable peaks the maximum possible thickness of the amorphous surface. The range of amorphous surface thicknesses found from the calculated diffraction profile is 12-20 A. This is in good agreement with complementary studies performed on the same crystal preparations.