STATIC AND DYNAMIC PROPERTIES OF POLYACRYLAMIDE GELS AND SOLUTIONS IN MIXTURES OF WATER AND GLYCEROL - A COMPARISON OF THE APPLICATION OF MEAN-FIELD AND SCALING THEORIES

The role of solvent in determining the static and dynamic behavior of polyacrylamide gels and solutions (c(PAA) = 5 %, c(bis) = 2.5 %) in mixtures of water and glycerol has been examined using light scattering methods. Increasing the glycerol content decreases the solvent quality for polyacrylamide and results in a lower second virial coefficient: 10(4)A2 (mol.ml.g-2) = 13.98 - 13.52-PHI, where PHI is the volume fraction of glycerol. Solutions and gels show closely similar behavior as regards dependence on solvent quality. The radius of gyration and hydrodynamic radius are experimentally related to the reduced temperature tau = (T - THETA)/T by R(g) approximately tau--0.08 and R(h) approximately tau--0.10, where THETA is the Flory temperature, whereas scaling theory predicts an exponent of -0.2. It was found that the dependence of the longitudinal osmotic modulus on the reduced temperature can be expressed M(os) approximately tau-0.58 for polyacrylamide solutions and gels, compared with the theoretical scaling exponent of 0.75 and a value of unity from mean-field theory. The friction coefficient between network and solvent increases strongly with increasing glycerol content in the solvent. The ratio of the friction coefficient to the viscosity of the solvent scaled as f/eta-0 approximately tau-0.45, which is close to the predicted scaling exponent of 0.5.