| Surfactant is a special substance with amphiphilic structure, which can be enriched on the interface and obviously change the property of the interface. The interface widely exists in nature and organism and closely relates with the life phenomenon, industrial production and daily life. Surfactants play an important role in the production of industry and agriculture and scientific research due to modulation and controlling the interface property as well as the production technics course on the interface.Zwitterionic surfactant not only has properties of conventional surfactants, but also has many unique properties, for example, the low toxicity and stimulating to the skin and the eyes, good biologic degradation, basically no social effects of pollution, in addition it is able to bear the hard water and the high concentration electrolyte. However, the difficulty of the preparation and high cost of zwitterionic surfactant limit its research and application. In recent years, the study and development of the zwitterionic surfactant cause much attention with the science and technology development, especially because of the high require for the mild kind of chemical commodity and environment protect. Not only the number but also the kinds of the zwitterionic surfactant rapidly increase and it has become the fastest developed kind of surfactant.This thesis studies the interaction between the zwitterionic surfactant dodecyl sulfobetain (SB-12) and the nonionic surfactant Triton-100, anionic surfactant sodium dodecyl sulphate (SDS) and cationic surfactant cetyltrimethyl ammonium bromide (CTAB) by means of surface tension measurements, fluorescence quenching and interface adsorption measurements. The change of the surface tension and critical micelle concentration (CMC) of the mixed system and the effects of different inorganic salts on the surface activity are carried out. The results are discussed according to the physical chemistry principle, which will provide some basic datum for the application of the zwitterionic surfactant mixed systems.1. The interaction between the SB-12 and Triton X-100It can be deduced from the surface tension isotherm that SB-12 and Triton X-100 can form the mixed micelle and the surface tension of the mixed system is between the surface tension of the single surfactant system. The interaction between SB-12 and Triton X-100 is similar with the surfactant similative, but it is stronger than that between the surfactant similative. The interaction parameter (β) are calculated according to the equation proposed by Rosen. The interaction between SB-12 and Triton X-100 molecules both in the micelle and in the interface are weak judging from the β values and it does not show the cooperative interaction. Inorganic salt has little effect on the surface activity of the mixed system, while the mixed system still has good salt resisted ability.The effect of SB-12 on the cloud point of TX-100 is also investigated. The results suggest that the cloud point of TX-100 obviously increased with addition of SB-12 and the cloud point changes with SB-12 concentration in line, which indicates the interaction exists between the two surfactants.The adsorption of SB-12, TX-100 and their mixed solution on the surface of polyethylene belong to Langmuir type. The maximum adsorption amount of SB-12 on the polyethylene surface rises with the addition of inorganic salt and the adsorption isotherm changes greatly. Especially when the salt concentration is from 0.005mol·L-1 to 0.1mol·L-1, two plateaus appear in the plot of the adsorption isotherm. The adsorption amount of the first one is below the maximum adsorption amount without the mono value inorganic salt. The second one is above the maximum adsorption amount without the mono value inorganic salt. However, inorganic salt has little effect on the saturation adsorption amount of TX-100, but the adsorption efficiency markedly increases and it has little relation with the salt concentration. For the mixed system, the adsorption isotherm and the saturation adsorption amount change a little with and without the mono valent inorganic salt, while the surfactant concentration corresponding to the saturation adsorption slightly increases for the divalent anion. In a word, the inorganic salt has no effect on the adsorption of SB-12/TX-100 on the polyethylene.The fluorescence spectroscopy results suggest that the I3/I1 values of the mixedsystems are all smaller than those of the single system, that is, the polarity of the mixed micelle is stronger than that formed by the two single surfactant system. It can be deduced from the fluorescence quenching the aggregation number of the micelle increases with the rise of the surfactant concentration and the average aggregation number of the mixed micelle is larger than that of the micelle formed only by SB-12 at the same surfactant concentration.2. The interaction between SB-12 and SDSThe surface tension isotherm of SB-12 and SDS shows that the CMC of the mixed system is smaller than that of the single surfactant system and the ability of forming micelle is enhanced when the two surfactants are mixed. The absolute β values of the mixed systems are all larger than that of the single system, indicating that there exists stronger interaction between the two surfactant molecules and the larger cooperative interaction of the mixed system.The CMC values obtained from the surface tension measurements and the fluorescence results are in good agreement, the CMC obtained from the fluorescence method is a little smaller than that obtained from the surface tension measurements. The I3/I1 value of the mixed system obviously smaller than that of the single surfactant system, that is, the polarity of the mixed micelle is markedly stronger than that formed by the two single surfactant system.We also investigate the effects of the inorganic salts on the mixed system, and find that the inorganic salt can promote the formation of the micelle and reduce the CMC value. The different salts with different valence have different effects on the mixed system of mixed surfactant systems. The ability to reduce the CMC values is: NaCl ≈ Na2SO4 < MgCl2 < AlCl3.3. The interaction between SB-12 and cationic surfactant CTABSB-12 and CTAB can be formed mixed micelles. The weak interaction exists between the both surfactants molecules. In solutions with different concentrations, the interaction parameters between SB-12 and CTAB, βS,βM are smaller negative values,even positive. The salt can promote the formation of the micelle and it can reduce the concentrations of CTAB and the CMC of mixed micelle. The values of CMC are almost same, which are got by surface tension and fluorescence methods. The value is little smaller by fluorescence than surface tension method.We calculated the charge distribution of SB-12 molecule by the ab initio method in quantum chemistry and the results show that SB-12 bear the high positive charge. So it is easy to bind with the SDS molecules with negative charge. The static force and hydrophobic interaction between the two molecules together result in the stronger cooperative interaction. The interaction between SB-12 and nonionic surfactant molecules is larger than that between SB-12 and CTAB molecules, which explains the results from the experiments.The novelty of the thesis is to study the complex rule of the zwitterionic surfactant and the anionic, cationic and the nonionic surfactants by interface activity measurement, interaction parameter calculation and ab intitio method in quantum chemistry. SB-12 is chosen as our studying object because it shows the zwitterionic property in all the pH range. The results suggest the conclusion in references that zwitterionic surfactants can mixed with all other types of surfactants and show the stronger cooperative interaction has its limitation. SB-12 can be used with anionic, cationic and nonionic surfactants, but the obvious cooperative interaction can only occur in the zwitterionic and anionic surfactant mixed systems. |
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