The optical behavior of spherulites in crystalline polymers. Part I. Calculation of theoretical extinction patterns in spherulites with twisting crystalline orientation

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Abstract
The extinction behavior of spherulites in many polymers and nonpolymers is shown to result from a characteristic twisting of crystal orientation acquired during growth. Extinction patterns are calculated for model spherulites consisting of radial fibers in which uniaxial or biaxial crystalline fibers twist regularly in a right‐ or left‐handed sense about the fiber axis. The results are in good agreement with observed extinction patterns in all of the following cases: diametral sections of three‐dimensional spherulites, diametral sections tilted on a Federow universal stage, and two‐dimensional spherulites grown in thin films. Details of this correlation will be given in Part II. Rules are given for (a) detecting the existence of twisting orientation, (b) determining whether it is of right‐ or left‐handed sense, and (c) determining the crystallographic axis about which twisting occurs.