Application of Interferometry to Analysis of Polymer-Polymer and Polymer-Solvent Interactions

For prediction of polymer systems behavior on processing and exploiting stages knowledge of phase diagrams is very useful and in some cases – necessary. They characterize equilibrium phase states and for particular systems – phase structure. Among other methods to estimate compatibility of two substances including polymeric one, and consequently to obtain reasonable information about phase state and structure of the final heterophase system, the optical interferometry method in a version of optical wedge (Borovskii et al, 1973; Malkin et al., 1983; Malkin&Chalykh, 1979; Avdeev, 1990; Chalykh & Gerasimov, 2004; Chalykh et al., 1998; Makarova, 2007) engages specific space. Each of components forms the intrinsic interference pattern with a pitch reciprocally proportional to its refraction index. Two components form two interference patterns separated by interface. As a result of interdiffusion, interference fringes close to the interface are bending. This process indicates on formation of solutions of various concentrations with their own refraction indices. Evolution of fringes shape in time gives the information about intensity of interpenetration of components allowing us to calculate the interdiffusion coefficients. Plotting concentration profiles at different temperatures and accepting that concentrations at the interface are equilibrium ones, it is possible to construct phase diagrams of binary systems.