Microstructure and rheology of polymer-surfactant solutions

Abstract

The rheological properties and microstructure of water-soluble polymer (hydrophobically modified hydroxyethyl cellulose, HMHEC) without/with addition of ionic and nonionic surfactants have been studied by viscometry and laser light scattering. The shear viscosity, viscoelastic properties and thixotropic properties are measured in terms of (1) HMHEC concentration (2) surfactant concentration at fixed HMHEC concentration (3) HMHEC concentration at fixed surfactant concentration (4) types of surfactants.The interactions between HMHEC and surfactants are also investigated via relaxation time and radius of gyration. The effect of temperature on the interaction between polymer and surfactant is also studied. It is found that the effect of HMHEC on the cloud point of nonionic surfactant is significant. Moreover the cloud point temperature has great influence on the rheological properties of polymer-surfactant systems. Although the polymer-surfactant system showed an Arrhenious dependence on temperature at temperatures far from the cloud point, the viscosity of polymer-surfactant systems shows markedly different at near to the cloud point temperature. The viscosity of mixed system increases with increasing temperature and reaches local maximum around their cloud point.