Flow behavior of poly(ethylene oxide)-laponite nanocomposite solutions

The flow behavior of poly(ethylene oxide) (PEO)-Laponite RD-water mixtures with polymer concentrations between 0.05 wt% and 1 wt% in the range of temperature 100C-50 degrees C is investigated. The evolution of the elastic modulus, the viscous modulus and the loss tangent as a function of oscillation frequency for the studied mixtures gives some indications about the dispersions structure. The rheological results allow to evidence of two critical concentrations: c(1)=0. 113 wt% PEO and c(2)=0.51 wt% PEO. Below 30 degrees C, all mixtures exhibit the gel-like properties. For concentrations lower than cl, the mixtures containing PEO are also the gels at temperatures above 30 degrees C. The structure for mixtures with PEO concentrations between c, and c(2) is strongly influenced by temperature and these systems are considered "critical gels" at temperature higher than 30 degrees C. The rheological behavior of the mixtures with the polymer concentration above c(2) is affected by the formation of PEO clusters at higher temperatures.