The Aggregating Behaviors Of Surfactants In Aqueous Solutions Studied By Nuclear Magnetic Resonance Technique

Recently, due to the extensive application of surfactant and their mixed systemswith different surfactants or with water-soluble polymer, i.e. the enhancement of oilrecovery and understanding the biologic mechanism etc., the study of theirphysical-chemistry properties in solution have received great attention. In this work,we mainly used the nuclear magnetic resonance spin-lattice relaxation time, spin-spinrelaxation time, diffusion coefficient and Two Dimension Nuclear Overhausespectroscopy techniques to study the aggregation behaviors of some surfactants inthree different typical surfactant systems. They are listed here respectively: (1) Thecomparison of the micellar structures between three pure surfactant aqueous solutionswith different molecular structures such as sodium alkylsulfates with normal,branched alkyl chains and with the polyethylene oxide chain inserted between thealkyl chain and the sulfate polar head; (2) Simulation of the NMR self-diffusioncoefficient experimental data of cationic-nonionic mixed solution (cetyl trimethylammonium bromide and triton X-100 surfactant) with different molar ratios,important parameters were obtained such as critical micelle concentration of the.mixed solutions and of the two individual surfactants, the interaction parameter,themixed micellar composition and the conformational changes of the ethylenegylcolchain on the TX-100 molecules at different CTAB molar ratios in their mixed aqueoussolutions. These results not only agreed with some previous results deduced from 2DNOESY experiments but also gave deeper insight into the mechanism of the mixedmicellization; (3) Finally, we discussed the interaction between polymer andsurfactant in their mixed aqueous solution. In the mixed solution of polyacrylamide(PAM) and sodium dodecylsulfate (SDS), the presence of polymer decreased the cmcof SDS. But the 2D NOESY experimental does not support the binding of SDS withthe polymer. The interaction between the benzyl oxide hydrophobic modifiedpolyacrylamide (PDAM) and SDS at two fixed concentrations of PDAM 10g/L and2g/L with various of SDS concentrations was studied by using the NMR self-diffusioncoefficients experiment, the different interactions were found. 2D NOESY experimental showed the co-aggregation between sodium dodecylsulfonate (SDSN)and polyethylene glycol (PEG).The above studies of surfactant aggregation behaviors in different aqueoussolutions, demonstrated the advantages of application of NMR technique to the studyof surfactant systems, such as the abilities of examining the dynamic characters ofsome definite groups, the directly binding information, etc.. The above results showthe merit of NMR technique in studing surfactant systems.