Properties Of Surfactant Mixtures Containing Gemini Component-photosensitive Rheology And Adsorption

This thesis consists of two aspects. One is light responsive rheological behaviorof C13pPHCNa/mAzo4N mixed system. The other is the synergy of Geminisurfactants/alcohols at the air/liquid interface. The mixed systems containing Geminisurfactants were chosen to study the influence of synergistic effect betweencomponents in bulk and interface phase. The abstracts are summarized as follows.Controlled fluids are important in many special fields. The system of wormlikemicelles has excellent rheological properties such as remarkable viscoelastic, highviscosity, shear-thinning behavior. Gemini surfactant can be designed with the uniquenature of the molecular structure, which can be regulated by molecular designflexibility to build wormlike micellar systems. Therefore, in the first aspect of thispaper, photorheological (PR) fluids were constructed by mixed anionic Geminisurfactant C13pPHCNa which could be easy to form wormlike micelle and traditionalcationic surfactants mAzo4N (m=0,4,8) with an azobenzene group in the alkylchain on account of synergy by changed the condition of UV-light irradiation. Theinfluence laws of factors such as the position of light functional group (azobenzenegroup) in the alkyl chain and the concentration of Gemini surfactant was get byanalyzing the spectroscopic of light functional group in different conditions and theproperties of steady-state and dynamic rheology. The main contents and conclusionsare summarized as follows:1. The viscoelastic wormlike micelles were formed by mixtures of cationicsurfactants mAzo4N and anionic Gemini surfactant C13pPHCNa in lowerconcentration.2. The structure of mAzo4N affected the properties of wormlike micelles, whichzero-shearing viscosity increases as m increases because of the synergy betweenC13pPHCNa and mAzo4N was enhanced and the effective molecular geometry ofmixed system was more beneficial to form wormlike micelle as m increases.3. The concentrations of C13pPHCNa affected the properties of wormlikemicelles. The viscoelasticity of the systems was strengthened through increasing the concentrations of C13pPHCNa which was the main component to construct thewormlike micelle.4. Synergy between C13pPHCNa and mAzo4N was changed after lightresponsive isomerization of azobenzene group in mAzo4N molecule happened underthe condition of UV-light irradiation, at the same time, the structures of mixedmicelles (such as the length of micelle, the overlap degree, the branching degree) werealso changed. The mixed system had the properties of light responsive rheology.5. The structure of mAzo4N affected the light responsive properties of rheology.The effect of light responsive isomerization of azobenzene group to synergy amongcomponents was weakened with m increasing. The light responsive isomerization ofthe system was also weakened.6. The concentration of C13pPHCNa in mixed system had an effect on theproperties of light responsive rheology which were weakened because the synergyamong components was enhanced as the concentration of C13pPHCNa increased andisomerized percent conversion of azobenzene group decreased.Mixed system of surfactants which containing Gemini surfactant was alwaysutilized on the practical application. Alcohols are the most common co-exist materialswith surfactants. Gemini surfactant has the higher aggregation ability, surface activityand other excellent properties due to the unique molecular structure (especially itsspacer chain) which will also impact on synergy between Gemini surfactant andalcohols to a great degree, thus affecting properties of mixed system. In the secondaspect of this paper, Quaternary Ammonium Gemini surfactants12-s-12(s representsthe number of methylene group; s=2,3,4,5,6) and hexanol were chosen to studythe adsorption of the mixed system at air/liquid interface.12-s-12is a number ofGemini surfactants with the most extensive investigation at present, which mostnotable feature is that its conformation is different with different length of flexiblehydrophobic spacer chain. Therefore, the influence of chain length on synergy inmixed system was studied and the influence of hexanol concentration on synergy wasalso discussed. The main work and conclusions are summarized as follows:1. Synergetic effect was occurred in the mixed system of Gemini surfactants/hexanol, which formed non-ideal mixed adsorption layer at the air/liquidinterface. 2. Hexanol in mixed system had been in majority in the bulk phase, but onlyslightly more than12-s-12in the mixed adsorption layer. It showed that theadsorption capacity of12-s-12is far stronger than hexanol.3. Hexanol had a strong effect on the adsorption of12-s-12at the air/liquidinterface. The strength of the effect depended on the length of spacer in12-s-12molecules. The adsorption capacity of the system was weakened withs increasing from2to4but enhanced with s from4to6in hexanol-watersolution.4. The adsorption capacity of the system and the synergetic effect betweenGemini surfactants and hexanol were both enhanced as increasingconcentrations of hexanol.5. The adsorption capacity of the mixed system of12-s-12/hexanol was notsensitive to the temperature.