On extinction patterns of polymer spherulites

Abstract

Abstract The extinction patterns between crossed nicols shown by two types of arrays of uniaxial crystals have been investigated. The arrays were ( a ) a disk whose radii were twisted arrangements of such crystallites, the plane of the disk being tilted at an arbitrary angle to the direction of observation, and ( b ) a cone of arbitrary apex angle whose sides were composed of twisted arrangements of crystallites, the cone being observed along the axis. The optic axes of the crystallites make an arbitrary but fixed angle with a radius of the disk or a ray of the cone. The extinction patterns of the disks can be circles, distorted displaced loops or zigzags, or mixtures of these, depending on the parameters. The extinction patterns of the conical arrays can be spirals or zigzags or both.