SOLUTION AND ADSORPTION PROPERTIES OF HYDROPHOBICALLY ASSOCIATING WATER-SOLUBLE POLYACRYLAMIDES

The behavior in aqueous solution and at a solid/liquid interface of an associating hydrophilic/hydrophobic copolymer of acrylamide and alkyl methacrylate has been studied. A comparison between the behavior of h ydrophobically associating and of non-associating polymers termed HAPA M and PAM, respectively of the same molecular weight indicates the rol e played by the hydrophobic moieties. Viscosity measurements in soluti on show the behavior expected of HAPAM compared to PAM i.e. a smaller intrinsic viscosity measured in the dilute regime and a larger viscosi ty in the semi-dilute regime. At the water/mineral interface, adsorpti on isotherms for HAPAM show an unusual shape, characterized by the abs ence of a plateau region and a continual increase in the adsorbed amou nt with polymer concentration in the bulk. The enhancement of polymer chain interactions in solution and the increase in the adsorbed amount on a mineral surface are observed within the same polymer concentrati on range. This particular adsorption shape can be explained by the for mation of multiple layers through hydrophobic associations, the adsorb ed layers being formed in part by some chains that are not directly in contact with the surface. The influence of KCl concentration has been studied. Modification of the polymer solution rheological properties and of the adsorbed amount of polymer leads to a strengthening of hydr ophobic interactions in the presence of KCl.