H-1-NMR INVESTIGATIONS OF THE INTERACTIONS BETWEEN ANIONIC SURFACTANTS AND HYDROPHOBICALLY-MODIFIED POLY(ACRYLAMIDE)S

The binding of alkylbenzenesulfonates to various hydrophobically modif ied poly(acrylamide)s which differ in the degree of hydrophobe modific ation has been studied by H-1 NMR. The extent of surfactant binding to copolymer, as evidenced by the change in chemical shift and line broa dening, was found to be dependent on the degree of hydrophobic substit ution. No evidence for surfactant binding was found in the unmodified poly(acrylamide). The exchange of the free surfactant between two site s, one corresponding to the free surfactant and the other correspondin g to surfactant bound to copolymer, was found to be fast on the H-1 NM R chemical shift time scale. The changes in line shape of certain peak s in the H-1 NMR spectrum of the surfactant were attributed to restric ted rotation of the aromatic ring of the surfactant as a result of bin ding to the copolymer.