No abstract

Dynamic light‐scattering measurements are reported for a medium‐density and a low‐density polyethylene. It is found that the scattering at small angles can be described in terms of the deformation of spherulites, whereas that at larger angles depends upon rearrangements of partially ordered crystals within the spherulites.

An apparatus and procedures are described for the observation of the light‐scattering changes during the periodic vibration of a polymer film sample. The relationship between static and dynamic scattering experiments is discussed as are the means for interpreting such experiments in terms of spherulite deformation and statistical theories. The performance of the apparatus is illustrated with some experiments on a medium‐density polyethylene sample.

Angular distribution of scattered ions at glancing angle incidence of 3 keV He ions on a (001) surface of GaAs is studied during its molecular beam epitaxial growth. We report observation of intensity oscillations of the scattered ions from the growing surface. The period of the oscillations corresponds to the growth time of one monomolecular layer. The oscillations of the intensity is due to the oscillatory change in surface step density during layer-by-layer growth of the surface. This observation is in agreement with the intensity oscillations of reflection high-energy electron diffraction (RHEED) from epitaxially growing surface of GaAs.

The change in the light‐scattering patterns upon deforming two‐dimensional disordered spherulites is shown to arise from four effects occurring upon stretching: (1) the change in shape of the spherulite, (2) the change in average orientation of the optic axes of the scattering volume elements, (3) the change in deviation of the optic axis orientation angle from its average value, and (4) the change in the distance over which this deviation is correlated. The effects of these contributions upon the experimental scattering patterns are analyzed.