Mutual macromolecular crowding as the basis for polymer solution non-ideality

Semidilute polymer solutions differ greatly from dilute solutions in properties such as viscosity, relaxation time, elastic modulus, colloid osmotic pressure, and light scattering. Previously, Matsuoka and Cowman proposed a single semiempirical expression for the nonideality contribution due to the concentration and intrinsic viscosity dependence, which has no other adjustable parameters, but quantitatively fits data for flexible, semiflexible, and rigid polymers in good solvents. In this report, the excluded volume theory as proposed by Ogston and Laurent is generalized to include mutual crowding between identical polymers based on hydrodynamic volumes, and applied to derive the expression for the nonideality contribution to specific viscosity, colloid osmotic pressure, and light scattering. Additionally, consideration of the contribution of mutual macromolecular crowding to the effective solvent viscosity allows prediction of polymer relaxation time and elastic modulus in semidilute solutions. This theoretical approach now allows the prediction of semidilute polymer solution properties based only on concentration and intrinsic viscosity, and conversely allows intrinsic viscosity (and thus average molecular weight) to be calculated from measurements made on semidilute solutions of known concentration.