NMR study on the micellar microstructures of three anionic surfactants with different molecular structures in aqueous solution

The comparison of the micellar microstructures among three pure surfactant aqueous solutions with different molecular structures such as sodium alkylsulfates with normal, branched alkyl chains and with the polyethylene oxide chain inserted between the alkyl chain and the sulfate polar head has been performed by using nuclear magnetic resonance spin-lattice relaxation time(t(1)), spin-spin relaxation time(t(2)), self-diffusion coefficient and two dimensional nuclear Overhause enhanced spectroscopy techniques. According to the ratios of t(2), to t(1) 1 the hydration layers of the micelles were deduced. The t(2)/t(1) values show that the hydrocarbon chains of surfactant II are more compact in the micelles than that of surfactant I. NMR self-diffusion coefficients show that the micelles formed from surfactant I are larger than those from surfactant R. At last, the 2D NOESY technique was applied to confirm the arrangement of the polyethylene oxide chains outside the hydrophobic micelles.