An Improved Infrared Method for Measuring Structure and Orientation in Polymers

Abstract

Infrared spectroscopic methods have previously been developed for measuring the amount of structure and degree of orientation in three dimensions in polymer films. These methods involved tilting the sample with respect to the radiation beam. For samples with little orientation the results were found to be extremely sensitive to the accuracy of the absorbance measurements made at the tilted angle. This tilted absorbance measurement was required to determine the refractive index and path length of the refracted beam in the sample. The error in this sensitive measurement was reduced by utilizing a refractive index obtained from a multiple of measurements. The precision of the measurements was improved by 50% by this change in the method and suggests a simplification of the procedure. The improved method was utilized to study uniaxially drawn polyacrylonitrile films. It was concluded that only partial uniaxial orientation of the film was obtained.