Langmuir, Vol.10, No.11, 4195-4202, 1994
H-2 NMR-Study of Hydrocarbons Adsorbed by Ion-Exchange Resins - The Effect of Surfactants
The interactions of two nonpolar molecules, deuterated cyclohexane and benzene, with two strong anion exchange resins have been examined using deuterium NMR spectroscopy. The observed spectra consisting of overlapping narrow and broad peaks, which can be attributed to free and adsorbed hydrocarbon molecules, respectively, show strong dependence on the nature of the exchange resin. The effect of a cationic surfactant, sodium cholate, on the observed spectra suggests that the bound surfactant molecules are capable of "solubilizing" hydrocarbons into the resin phase. Longitudinal relaxation times were measured as a function of temperature at two different magnetic field strengths. The results reveal the presence of fast and slow molecular motions similar td those observed in other restricted systems such as micellar solutions and lipid bilayers. The data were further analyzed in terms of the two-step model, involving fast slightly anisotropic motions superimposed upon slow isotropic motions.
Keywords:NUCLEAR-MAGNETIC-RESONANCE;ALKYL-MODIFIED SILICA;C-13 NMR;WATER INTERFACE;BILE-ACIDS;HETEROGENEOUS SYSTEMS;ANIONIC SURFACTANTS;POLYMERIC SORBENTS;MICELLAR SOLUTIONS;RELAXATION