Interferometric studies in diffusion. I. Determination of concentration distributions

Abstract

An interferometer technique for the quantitative study of swelling and diffusion in transparent high polymers and a method of determining the concentration distribution from the fringe system have been developed. The concentration—distance curves in the system chloroform-stretched cellulose acetate have been determined at two different temperatures with a view to estimating activation energies over a range of concentrations. The curves are found to consist of two almost linear portions with a considerable and abrupt change of gradient taking place over a small range of concentration. A corresponding sudden change of gradient has been observed in other systems. Considerable experimental difficulties were met in determining the refractive index and density curves for the two component systems, which were required by the method. Eventually a refractive index curve was constructed with the help of data obtained by several approaches.