Influence of an adsorbing polymer on the aging dynamics of Laponite clay suspensions

Clay-polymer dispersions in aqueous solutions are of great interest due to their industrial applications and intriguing physical properties. Aqueous solutions of bare Laponite particles age spontaneously, from an ergodic to a non-ergodic state, in a time varying from hours to months depending on Laponite concentration. When a polymer species, such as polyethylene oxide (PEO), is added to the solution, it weakly adsorbs on clay particle surfaces modifying the effective interaction potential between Laponite particles. A dynamic light-scattering study was performed to investigate the effect of polymer on the aging dynamics of the system by varying the polymer concentration at a fixed polymer molecular weight (M-w = 200,000 g/mol). The results show that arresting phenomena between clay particles are hindered when PEO is added and, thus, a slowing of the aging dynamics with increasing PEO concentration is observed. A possible mechanism is progressive coverage of the clay surface by polymers, which grow with increasing PEO concentration.