Study of the concentration dependence of the viscosity of dilute polymer solutions. Compression of polymer chains

Abstract

STUDY of the hydrodynamic and thermodynamic properties of polymer solutions is an important task for practical reasons and is also of considerable theoretical value. The properties of infinitely dilute polymer solutions have been studied fairly thoroughly, both theoretically and experimentally. The derived theories of viscosity, light scattering, diffusion and sedimentation, and flow birefringence at c-+0 satisfactorily fit the existing experimental material and permit determination of the molecular weight, dimensions, shape and other molecular parameters of individual polymer chains [1]. The situation is different with regard to the concentration dependence of the hydrodynamic and optical properties of polymer solutions. Theories of the dependence of these properties on the concentration of polymer solutions have been derived only for the low concentration region, or more correctly for low values of c[t/], and these fit the experimental data only qualitatively. The properties of polymer solutions are dependent to some extent on the dimensions of the polymer chains, therefore for construction of the concentration dependence of their hydrodynamic and optical properties it is necessary to take account also of the dependence of the dimensions of the polymer chain on the concentration of the solution. The dimensions of polymer coils in solution are determined not only by entropic factors, but also by the energetics of polymer-solvent and polymerpolymer interaction. In good solvents these interactions result in effective mutual repulsion of polymer chain segments. The result of this is both increase in the size of the coils in comparison with the size in an ideal solvent, and also compression of the coils as a consequence of intermolecular interaction [2-4]. One of the methods of estimating the compression of polymer coils is by study of the viscosity of dilute polymer solutions. The first a t tempt at estimating the comression of polymer coils was made in reference [5]. The present work is devoted to development of a method of estimating the compression of