Aggregation And Properties Of Mixed Surfactant Systems

Surfactant is an amphiphilic substance. The characteristic of high efficiency to reduce the surface tension makes it playing an important role in the application of daily life. And its application can relate to almost all areas of fine chemicals. Under suitable conditions, surfactant molecular can form diverse aggregates, such as micelles and liquid crystals. In practical application, the performance of the surfactant mixed systems is more excellent than pure surfactant system. Mixed systems usually embody higher surface activity, richer phase behavior and more favorable environmental effects.In this paper, we studied the mixed micelles formed by anionic surfactant sodium oleate(NaOL) and three anionic surfactants of different structures(sodium deoxycholate NaDC, sodium bis(2-ethylhexyl) sulfosuccinate AOT and sodium lauryl sulfate SDS) and lyotropic liquid crystal formed by NaDC and C18:1E10. The main contents are as follows:Firstly, we studied the mixed micelles formed by anionic surfactant NaOL and three anionic surfactants NaDC, AOT, SDS under different conditions. The results showed that the surface activity of NaOL/NaDC mixed systems increase with the increasing of concentration of salt medium. The values of interaction parameters ?m in NaSa medium are larger than other media which is between-3.59~-7.36. There is an interesting phenomenon of double inflections in the three mixed systems in 0.01 mol/L Na Cl media. The double inflection appeared at larger ?NaOL. However, in the buffer solution of pH 8 and 12, there are not double inflections for NaOL/NaDC system. By comparing the measured CMC values with the ideal CMC values, we found that all the mixed systems showed nonideality. The negative |?m| and |?m|>|ln(CMC1/CMC2)| proved synergies in NaOL/AOT system at ?1=0.17, NaOL/SDS system at ?1=0.17, 0.83 and NaOL/NaDC system at ?1=0.17, 0.83.Secondly, we measured some basic properties of the three anionic surfactant mixed systems, such as Krafft points, the calcium stability, lime soap dispersing power, foaming property and the solubilization of drugs. The results show that the Krafft point of 1% NaOL is 1.5 oC. Due to the Krafft point of NaDC is less than 0 oC, Krafft point of NaOL / NaDC mixed system are all less than 0 oC which indicate a good solubility. The Krafft points of NaOL/AOT, NaOL/SDS mixed systems are also less than 0 oC at large mole fraction. The calcium stability of NaOL/NaDC mixed system is poor. For NaOL/AOT system, although the calcium stability of pure AOT is strong, the stability of the mixed systems is worse than the pure AOT. The LSDP values of NaOL/AOT mixed systems are less than pure AOT which means strong lime soap dispersing ability for NaOL/AOT mixed system. Curcumin solubilization experiments show that the solubilization of pure NaDC is stronger than the other pure systems. For NaOL/ NaDC and NaOL/SDS mixed system, the solubilization is the strongest when ?NaOL=0.33. The NaOL/AOT mixed system did not show more obviously solubilization than pure NaOL.Finally, IPM and PEG 400 was added to the mixed system of C18: 1E10-NaDC as an oil phase to build a cubic crystal. We studied the effect of different factors on the microstructures of lyotropic liquid crystal by small angle X-ray scattering(SAXS). Then, we investigated the dynamic and steady rheological properties of the lyotropic liquid crystal by the means of rheology technology. We also investigated the release and stability of curcumin. Research results have shown that the cubic lyotropic liquid crystal can still maintain the original configuration after the adding of curcumin. Stability results showed that all of the cubic lyotropic liquid crystal entrapping curcumin exhibited shear thinning behavior. Dynamic rheological results showed that the characteristic relaxation time of the cubic lyotropic liquid crystal entrapping curcumin is longer than blank liquid crystal samples. Release and stability studies show that the cubic lyotropic liquid crystal entrapping curcumin of different PEG 400 content has a good release effect.