Measurements of Anisotropic Light Scattering and Thermal Transition in Optical Anisotropy of Poly-α-methylstyrene

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Abstract
The anisotropicoptical scattering from solutions of flexible macromolecules is discussed, and a simple experimental method of obtaining information concerning the optical anisotropy of a segment is presented. Intensities of anisotropic and isotropic optical scattering have been measured on poly‐α‐methylstyrene samples in the ranges of molecular weight from 400 thousand to 7 million, in trans‐decalin at 9.6° (theta temperature), 20.2°, 29.5°, 49.7°, and 91.6°C. Analysis of the experimental data by the present method shows that the optical anisotropy of poly‐α‐methylstyrene exhibits a transitionlike decrease with temperature with the midpoint of about 30°C. The origin of the slight cooperativity of the transition is discussed and concluded as indicative of the correlation between the skeletal bond rotation and the rotational motion of the phenyl group. Some change of the unperturbed mean‐square radius of gyration with temperature is suggested as a possible consequence of the transition.