Solvent-induced crystallization of polyethylene terephthalate

Structural implications of small-angle light scattering from cornea.

Porous structure of crystalline polymers by exclusion effect of carbon dioxide

A combination of in situ birefringence and depolarized light-scattering experiments was used to study the formation of an ordered cylindrical microstructure in a polystyrene-block-polyisoprene copolymer melt under a shear flow field. We demonstrate that our sample forms an imperfect “single crystal” with a fraction of the cylinders aligned in the flow direction. The aligned regions of the sample coexist with randomly oriented grains. The birefringence experiments enable the characterization of the aligned regions while the depolarized light-scattering experiments enable the characterization of the randomly oriented grains. A model for depolarized light scattering from such samples was developed. It was shown that the usual scattering formulas for grains embedded in an isotropic matrix are applicable provided one recognizes that the scattering vector, q, has transverse (qT) and longitudinal (qL) components even in the small angle scattering limit (qL is the component of q in the propagation direction). Thi...

Birefringence and Depolarized Light Scattering of an Ordered Block Copolymer Melt under Shear Flow

The measurement of optical anisotropy is one of the simplest and most exploited methods of studying orientation in polymers. It depends on the fact that a given material has associated with it unique optical properties determined by its polarisability.

Physico-Chemical Approaches to the Measurement of Anisotropy

The scattering of light by a two-dimensional spherulite of radius R is calculated when there is disorder of optic axis orientation with respect to the radius. Special cases are considered when (1) the disorder occurs in the radial direction only, (2) the disorder occurs in the angular direction only, (3) there is combined radial and angular disorder, and (4) the optic axis makes a constant angle with the radius but there is disorder in the twist angle about the axis. In all of these calculations, a correlation function for disorder is defined and the scattering pattern depends on the ratio of the associated correlation distance to the size of the spherulite. With decreasing correlation distance, the azimuthal dependence of the scattering becomes less and there is a change in the variation of scattered intensity with scattering angles in a manner dependent upon the type of disorder.

Scattering of light by disordered spherulites

: The effect of birefringence of a polymer film upon its photographic light scattering pattern is considered for the case of a single anisotropic two-dimensional spherulite imbedded in a birefringent matrix. It is shown that for the case of a polarizer and analyzer crossed at +45 deg. and -45 deg. to the analyzer the scattering pattern is modified in a manner agreeing with experimental observation. (Author)

W. Chu

Papers

Scattering of light by disordered spherulites

Effect of birefringence on low-angle light-scattering patterns from oriented polymer films. II