VISCOELASTIC PROPERTIES OF LAPONITE RD DISPERSIONS CONTAINING PEO WITH DIFFERENT MOLECULAR WEIGHTS

The effect of poly(ethylene oxide) (PEO) molecular weight on the viscoelastic properties of Laponite RD aqueous dispersion at 25 degrees C was investigated and discussed. PEO with molecular weight between 0.4x10(3) g/mol and 35x10(3) g/mol was added in concentration of 2% into 2.5% clay aqueous dispersion. The addition of polymer with molecular weight above 4x10(3) g/mol delays the transition from liquid to colloid glass state. It was established that there is a critical molecular weight of added poly(ethylene oxide) which depends on the components concentrations in dispersion from which one chain becomes able to bridge two or more clay particles. The critical PEO molecular weight established by the theoretical calculations considering the molecular weight or the polymer concentration was about 21.45x10(3) g/mol and 25x10(3) g/mol, respectively. The experimental data obtained by rheological measurements were in agreement with theoretical approaches.