Interaction between a tertiary amine methacrylate based polyelectrolyte and a sodium montmorillonite dispersion and its rheological and colloidal properties

The rheological and colloidal properties of sodium montmorillonite dispersions were investigated in the presence of a special type of cationic polymer [modified poly(ethylene glycol)]. 2‐(Dimethylamino) ethyl methacrylate was polymerized with monomethoxy‐capped oligo(ethylene glycol) via aqueous atom transfer radical polymerization. The tertiary amine residues of the resulting polymer were then quaternized with methyl iodide to obtain a cationic polyelectrolyte. The rheology and ζ‐potential experiments showed that the cationic polymer adsorbed onto the sodium montmorillonite surface strongly. The rheological parameters (plastic viscosity and yield value) were obtained with a rotational low‐shear rheometer. The results indicated a gradual increase in gelation with the addition of the cationic polymer, which reached a maximum at a cationic polymer concentration of 0.4–0.8 g/L. This gel‐like dispersion showed pronounced thixotropy. A further increase in the polymer concentration resulted in a reduction in this gelation. The adsorption of the cationic polymer onto the clay surface reduced the ζ potential to small values, but no isoelectric point was observed. The basal‐spacing measurements showed that the cationic polymer strongly adsorbed onto the sodium montmorillonite instead of entering the montmorillonite layers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 300–306, 2005