Double Refraction of Flow: Numerical Evaluation of Extinction Angle and Birefringence as a Function of Velocity Gradient

The method of double refraction of flow in systems containing large asymmetrical molecules gives experimental data which, when interpreted in light of the theory of Peterlin and Stuart, enable one to calculate molecular lengths; information about the polydispersity of the system and about the optical properties of the solute particles may also be obtained from such data. Heretofore, this theory had been developed so that the data could be interpreted only under the limiting condition of low velocity gradient where the degree of orientation of the solute particles is very small. With the aid of the Mark I computer of the Harvard Computation Laboratory, the necessary equations have been solved to provide numerical values over a much wider range of velocity gradients, greatly increasing the usefulness of flow birefringence measurements for the study of macromolecular systems.