Apparatus for the measurement of electro-optical rotation changes in polymer solutions

Abstract

With highly asymmetric macromolecules, the observed optical activity depends upon the orientation of the molecules relative to the propagation direction of incident, linearly polarised light. Application of a pulsed electric field is accompanied by transient changes in the optical rotation. A laser-based apparatus has been assembled to measure these small changes with high precision. Details of the system are described along with the theoretical considerations upon which the design was established. The performance of the apparatus is demonstrated by measurements on solutions of the alpha -helical polypeptide poly- gamma -benzyl-L-glutamate in dichlorethane. The sensitivity of the measurements far exceeds all previous estimations of the rotatory powers associated with the alpha -helical axial directions.