Viscosity and osmotic second virial coefficient of maleic acid copolymers in aqueous solutions

Abstract

Unperturbed dimensions or characteristic ratios of maleic acid copolymers (MA-copolymers) in aqueous solutions were estimated for various degrees of neutralization, α, to clarify the abnormal α-dependence of viscosity of MA-copolymers in more detail. The dependence of the osmotic second virial coefficient A 2 on α was measured in NaCl aqueous solution. A 2 was analysed by the Fixman-Skolnick theory on account of the activity coefficients of counterions at various α's. The characteristic ratio seems nearly constant, ∼ 10, independent of α, and the maximum at α = 0.5 is not observed. A 2 increases with increase of α up to α = 0.5 and decreases with further increase in a corresponding to the α-dependence of viscosity. Fairly good agreement between the experimental and theoretical values of A 2 is observed. Theoretical values of A 2, however, increase monotonically with increase in α. Our experimental results show that the α-dependences of viscosity and A 2 of MA-copolymers in aqueous solutions should be attributed to a change of hydration structure of the pair of adjacent carboxyl groups with neutralization.