Gemini-like Surfactant Constructed By Electrostatic Interaction And Synergism Of Surfactant Mixtures Containing A Gemini Component

This thesis consists of two aspects that both focus on the gemini surfactant. Oneaspect is to construct gemini-like surfactant systems using the most commonconventional surfactant SDS and to investigate the rheological behavior of thewormlike micellar systems. The other aspect is devoted to the synergy of the cationicsurfactant mixtures containing a gemini component. The abstracts of both aspects areexpressed as follows.Wormlike micellar systems are important in both industry and academic aspctsand attract more and more attention due to their remarkable properties. A surfactantwormlike micellar system has strong solubilization capacity, excellent rheologicalproperties such as high viscosity, remarkable viscoelastic, shear-thinking behavior,and the unique rheology characteristic as a result of the rapid breaking andrecombination dynamic equilibrium of the wormlike micelles that so called “livingpolymers”, and so on. However, for the limitation of the molecular geometry,conventional surfactants are hard to form wormlike micells unless at a rather highconcentration or in the presence of additives such as co-surfactants and salt.Comparatively, gemini surfactants has a unique molecular structure, whosemolecular geometry can be regulated to meet the requirements for the formation ofwormlike micelles. Nevertheless, the high cost and the difficulty in synthesis greatlyprevent the use of gemini surfactants. If a gemini surfactant can be constructed notwith synthesis but with linking two common conventional surfactant molecules witha non-covalent bond, it is no doubt that the application of gemini surfactant in bothindustry and academic field will be greatly widenned. In this thesis, gemini units ofsurfactant are constructed with the most common conventional surfactant SDS andthe bola type counterions by electrostatic force. The gemini-like surfactant systemsshow high surface activity and strong ability of aggregateion similar to the geminisurfactant systems. When the spacer of the bola counterion is short (two methylenegroups), the system forms wormlike micelles and shows viscosielastic behavior,whereas SDS alone only form spherical micelles enven when the concentration israther high. The main contents and conclusions of this work are summarized as follows:1. The special structure of bola salt and the electrostatic interaction with SDSare used to assemble gemini-like system systems, making SDS (the moleculargeometry of SDS fit to generate spherical micelle) form the wormlike micelle, whosesystem shows visoelastic property.2. The gemini-like system systems built by SDS and bola salt have propertiessimilar to gemini surfactants, such as high surface activity and strong aggregateability.3. Investigation to the influence of different inorganic and organic salts on theadsorption and aggregation of SDS indicate that the bola salt and SDS buildgemini-like system. Bola salt has higher effects on promoting the adsorption andaggregation of SDS.4. Similar to gemini surfactants, the gemini-like surfactant system built by SDSand bola salt also shows the dependence on the effect of space length.Assumption of building gemini-like system by the electrostatic interaction wasfirst proposed in this thesis and a preliminary attempt was made through the mostcommon commercialize surfactants and bola salt.The results show that the aboveconceive is feasible.Mixed system was always utilized by surfactant on its application. Thesurfactants with the same electrical property are not easy to produce precipitationand surfactant products are often mixture of homologues, therefore, it is highlysignificiant to study the aggregation behavior of the surfactants with the sameelectrical property.Conventionally, mixed system aggregation behavior ofhomologues is considred as an ideal one because of the similarity of the molecularstructure with each other. However, recent research proposed a different viewpoint,mixed system milicellar of homologues only with the different length of alkyl chainsdidn’t fully conform the ideal mixed behavior. And this behavior was not onlyaffected by the electrostatic interaction between the head group and the hydrophobicinteraction between alkyl chains, but also probably varied factors. Gemini surfactanthas the higher surface activity, aggregation ability and other excellent properties thanthe corresponding traditional one due to the unique molecular structure.The rule ofthe aggregation behavior between gemini surfactant and the other surfactant with thesame electrical property is the basis of gemini surfactant application. In this paper,Quaternary Ammonium gemini surfactants with the most extensive investigation, C12-2-C122Br dimethylene-1,2-bis(dodecyldimethylammonium bromide andCmTMABr (alkyltrimethylammomium bromide)(m=12,14,16)andC12TYABr(Y=-CH3,-CH2CH3,-CH2CH2CH3), was chosen to study theirmicellization of the mixed system and the influence of chain length and head groupsize of the traditional surfactant alkyl on the micellization of the mixed system wasalso discussed.The main work and conclusions are summarized as follows:1. Mixed micellization of aqueous solution of dimeric surfactant C12-2-C122Brwith the same electrical property and traditional surfactant CmTMABr (m=12,14,16)or C12TYABr(Y=-CH3,-CH2CH3,-CH2CH2CH3) shows non-ideal mixing.Theinterattraction of the two-component in the the mixed system promoted the processof micellization.2. The interattraction of the two-component in the mixed system ofC12-2-C122Br/CmTMABr decreased with increasing the alkyl length in CmTMABr.3. The interattraction of the two-component in the mixed system ofC12-2-C122Br/C12TYABr increased with increasing the size of Y group.4. C12-2-C122Br accounts for the main component in the mixed micelles ofC12-2-C122Br/CmTMAB and C12-2-C122Br/C12TYABr mixed system.5. Small amount of addition of dimeric surfactants can greatly reduce thecritical micelle concentration of traditional surfactants, making dimeric surfactantshave a extensive application.The above results illustate that the synergies in the process of ion surfactantmixtures micellization has association with not only electrostatic interaction betweenthe head group, hydrophobic interaction between alkyl chains, but also the moleculargeometry and conformation, molecular arrangement of micelles, etc.