VISCOMETRIC STUDY OF MIXTURES OF NEUTRAL AND CHARGED POLYMERS IN AQUEOUS-SOLUTION

The viscosity behaviour of aqueous mixtures formed by a polyelectrolyt e (A) and a neutral polymer (B) such as polystyrene sulfonate (PSS)-po lyvinylpyrrolidone (PVP) and polylysine (PLL)-PVP has been studied at 25 degrees C. The intrinsic viscosity and viscosity interaction parame ter of each polymer in water have been determined and have served us t o estimate the compatibility of the different mixtures according to tw o different methodologies: (i) mixtures of two polymers in water as so lvent and (ii) mixtures of either polymer A or B in a solvent formed b y either polymer B or A in water (''polymer solvent method''). By comp aring the experimental and theoretical viscosity data it is clearly se en that: mixtures of both polymers in water do not depict any kind of thermodynamic interaction; whereas mixtures formed by a polyelectrolyt e in water + neutral polymer as solvent exhibit incompatibility and, o n the other hand, ternary systems formed by the neutral polymer (PVP) in a polyelectrolyte solvent show compatibility. The viscosity results show that the compatibility behaviour depends on the concentration ra tio of both polymers in the mixture. Finally, an attempt to establish reference systems has been made. (C) 1997 Elsevier Science Ltd.