NMR Study Of The Complex Systems Of NP-10 And A Series Of Non-ionic Surfactants

Because of its special two affinity structure, the surface active agent can be used to adjust and change the physical and chemical properties of the interface, and it has very high application value and attracts considerable attention. But in the practical application, the surface active agent is used in the form of the complex system.Primarily because the combination of two kinds of surfactants can produce synergistic effect and has better application effect. Therefore, it is necessary to study the structural characteristics, dynamic properties and the interaction of the complex system. In this paper, the structural characteristics, dynamic properties and molecular interactions of three binary surfactants were studied by using NMR technics.The surfactant nonylphenol ethoxylates(NP-10) respectively and n-dodecyl-β-D-maltoside(DM), polyoxyethylene(40) sorbitan monopalmitate(T40)or six polyethylene glycol monodecyl ether(C10E6) form binary mixtures. Their dynamic performances, the intermolecular correlation points, the arrangements and the best ratios were investigated by some measures, including 1H NMR, self-diffusion coefficient(DOSY), relaxation time(T1 and T2) and 2D NOESY experiments.Chemical shifts(δ) changes in 1H NMR spectrum show that all proton move toward low field chemical environment changes in NP-10/DM system forming mixed micelles, its benzene chemical environment changes largest. With the increase in the total concentration of NP-10/T40 system, the majority of protons δ move toward low field, T1 proton has moved upfield. In NP-10/C10E6 system δ values all proton move toward low field, in which δ values of the proton N6, N7 and C4 change obvious due to the experience from single molecules to aggregate formation process.DOSY experiments revealed that D values of three binary surfactants has a tendency to become larger with the increase of temperature. The difference is, when the concentration of NP-10 was 5.9 mmol/L, the hydration kinetic radius of the mixed micelle increased with the increase of the amount of DM. The change trend is more and more slowly, until the NP-10 and DM molar ratio is 1:6, and then tends to be stable. In the mixed micelles of NP-10/T40 and NP-10/C10E6, the self-diffusioncoefficient were approximately equal to 3.563×10-11 m2/s and 6.083×10-11 m2/s after NP-10 and T40(C10E6) molar ratio is 1:8.The experimental results of 2D NOESY showed that the two molecules in the NP-10/DM system had five distinct intermolecular correlation points to form a mixed micelle. The arrangement for side by side relative arrangement in the mixed micelle.There are many intermolecular correlation points in the NP-10/T40 system. The benzene ring part of NP-10 molecule interact with five-membered ring of T40 molecule and partial nonpolar protons respectively forms mixed micelle. There are also many intermolecular correlation points in the NP-10/C10E6 system. The nonpolar part of C10E6 molecule interact with benzene ring part of NP-10 molecule relative arrangement in micelles. The transverse relaxation time(T2) results show that there are three binary complex systems in the presence of intermolecular interactions,and in the range of 1:1/2~1:1 molar ratio, 1:1/2 and 1:4, the interaction between the molecules is stronger, the synergistic effect is better. The best matching result is in agreement with the NOESY experiments. And TR(T2/T1) values showed that the three mixed micelles are closely packed. A comparative analysis of the interaction between three kinds of mixed micelles combined with 2D NOESY experiments. It is concluded that the interaction of NP-10/T40 and NP-10/C10E6 are stronger than that of NP-10/DM, and they can form a more stable mixed micelles.