MOLECULAR-DYNAMICS IN DILUTE AQUEOUS-SOLUTIONS OF ETHYL(HYDROXYETHYL)CELLULOSE AND SODIUM DODECYL-SULFATE AS INVESTIGATED BY PROTON NMR RELAXATION

Dilute aqueous solutions of ethyl(hydroxyethyl)cellulose (EHEC) and so dium dodecyl sulfate (SDS) have been investigated by H-1 NMR shift and relaxation measurements. The shift measurements indicate no presence of EHEC at the core of the SDS micelles but at and just inside the mic ellar surface. Both the spin-lattice relaxation time (T-1) and the spi n-spin relaxation time (T-2) imply that molecular motions slow as the system aggregates. T-1 measured at both 270 and 400 MHz indicates none xtreme narrowing conditions with molecular motions on the nanosecond t ime scale. T-2 monitors slower dynamics of the EHEC/SDS/ water as comp ared to both of the systems polyethylene oxide (PEO)/SDS/water and SDS /water, attributed to the rigid EHEC backbone as compared to the more flexible PEO chain. An important observation is that the NMR relaxatio n data correlate well with the microviscosity in the EHEC/SDS/water sy stem as measured by intramolecular excimer formation of the fluorescen t probe 1,3-di(1-pyrenyl)propane (P3P).