ADSORPTION OF HYDROPHOBICALLY ASSOCIATING POLYACRYLAMIDES ON CLAY

Compositionally homogeneous modified polyacrylamides were synthesized by micellar copolymerization leading to hydrophobically associating po lymers with a large range of viscosifying properties. The strength of the hydrophobic associations depends on the structure of the hydrophob ic comonomer and its distribution. Hydrophobic comonomers with a bulky structure lead to particularly strong thickening properties. Contrary to polyacrylamides that present a classical high affinity adsorption isotherm on alumino silicate surface, the adsorption of hydrophobicall y modified polymers increases with polymer concentration. The effect i s observed even if no intermocular associations are evidenced in solut ion. The bound fraction of water was determined by H-1 NMR, thus givin g indirect information on the adsorbed layer structure. Some modified polymers nearly completely replace the bound water, forming a quasi im penetrable adsorbed layer.