NMR Studies of Interactions between Neutral Polymers and Anionic Surfactants in Aqueous Solution

Abstract

NMR studies of aggregation phenomena in polymer-surfactant systems are reviewed. Such studies have included H-l, C-13, and F-19 chemical shift measurements on both polymers and surfactants, various relaxation time measurements, the dependence of spin-lattice relaxation rate on environment, and nuclear Overhauser enhancement (NOE) measurements. In the system PEO (polyethylene oxide)/SDS (sodium dodecyl sulfate) the paramagnetic relaxation method is used to determine the fraction of PEO monomer units bound in the aggregate. It is found that at low polymer concentration about 85% of the PEO is not exposed to the aqueous phase. At high PEO concentration the SDS micelles are saturated with approximately 1.9 EO monomers per surfactant molecule. Aromatic ring current shift measurements in systems containing ω-phenyldecanoate and water soluble polymers of varying hydrophobicity show that the degree of interaction of polymers with anionic micelles is governed by hydrophobic interactions between the polymer and the surfactant chain.