The Nuclear Magnetic Resonance (NMR) Study For The Complex Systems Of Tween40and Cationic Surfactants

The system of mixed surfactants known as the “industrial monosodium glutamate” has greatpractical significance. The mixed systems are much better than the single system. In the mixedsystems there is a lower critical micellar concentration (CMC), a fewer disage of surfactants, awide range of stable structures, higher stability and a superior performance. Polyoxyethylenesorbitan palmitate (tween40) is a common kind of non-ionic surfactants. It is a kind of stabilizingagents, a kind of wetting agents, a kind of dispersants, also a kind of antistatic agents and so on.There is a synergistic effect when putting them together. So to grasp the interaction between themolecules, their dynamic behavior, the mixed proportion and the complex structures is veryimportant.It is widely used to detect penetrates without destroying the sample itself by Nuclearmagnetic resonance technology (NMR) as a rapid, simple, accurate also recyclable method. NMRstudy for the mixed system of non-ionic surfactant tween40with other surfactants don’t bereported nor studied so far. NMR technology is effective for the study of the mixed systems ofnon-ionic surfactant polyoxyethylene sorbitan palmitate(tween40) with cationic surfactantdodecyl ammonium chloride (DTAC) and a series of gemini surfactants such as1,4-double(dodecyl ammonium chloride)(12-4-12), four methylene1,4-double(myristylchloride)(14-4-14),eight methylene1,8-double(dodecyl ammonium chloride)(12-8-12). Thispaper analyzes them qualitatively and quantitatively in detail. Experimental tests include the testof chemical shift, the longitudinal relaxation time T1, transverse relaxation time T2, T2/T1,self-diffusion coefficients (by Dosy) and the diffusion coefficient of the system (bytwo-dimensional NOESY). T2of the mixed system changes in the opposite trend with a brokenline when increasing of the concentration.The result reflects that the mixed micelles form andintermolecular interaction force of the mixed micelles appears. The value of T2/T1indicateshow closely the mixed micelles exist. The experiments of Dosy show that the cationic surfactantsdetermines the size of the mixed micellar radius and the radius increases then keep essentiallyunchanged.2D NOESY proves that the system of intermolecular interaction forces from big tosmall is tween40/14-4-14> tween40/12-4-12> tween40/12-8-12> tween40/DTAC. We aslocan infer the mixed micelles stereochemistry is the tail chain of tween40connects the tail chainand ionic head group of the traditional cationic surfactant while the tail chain embeds the lumen of the three Gemini cationic surfactants. Generally speaking, Gemini surfactants reflect superiorproperties than the traditional ones. The molecular interactions significantly increase byincreasing the tail chain alkanes of Gemini surfactants and down a bit by increasing the the linkchain (space) of Gemini surfactants. The optical molar ratio between tween40and Geminisurfactants is2.5:1while3.5:1with DTAC.