| It always attracts much interest to investigate and synthesize novel surfactantswith high surface activity. In the last two decades, the most representative result wasthe synthesis of Gemini surfactants with high surface activity and rich structuraldiversity of aggregation. For the quaternary ammonium salt Gemini surfactants, inaddition to changing the spacer and tail chains, changing the headgroups by bondingdifferent alky chains is also an effective mean to regulate their aggregation behavior.To study the effects of headgroups structures on the performance and aggregationbehavior of quaternary ammonium salt Gemini surfactants, it not only can enrich thetheoretical knowledge about the self-assembly behavior of Gemini surfactantmolecules, but also lay the foundation for the application of Gemini surfactants in manyfields. For this reason, we synthesized three series of novel cationic Gemini surfactantswith long chain alkyl ammonium headgroups and studied their surface activity,aggregation behavior and related application. In this thesis, the long alky chains refer tothe ethyl, the n-propyl and the n-butyl which are longer than the methyl. These seriesinclude the Gemini surfactants with long chain alkyl ammonium headgroups andmethylene spacer (CmCsCm(Cn)Br2), the Gemini surfactants with diethylammoniumheadgroups and diamido spacer (CmC2ONC2NOC2Cm(C2)Cl2), and the Geminisurfactants with diethylammonium headgroups and diester spacer(CmC2OOC2OOC2Cm(C2)Cl2), where m represents the number of carbon atoms of thetail chain, s represents the number of carbon atoms of the spacer, and n represents thenumber of carbon atoms of the alkyl chain of headgroups.The main content and conclusions in this thesis are divided into the followingparts:(1) Based on the overview of the syntheses, properties and applications of Geminisurfactants, the research ideas were proposed.(2) Three series of novel Gemini surfactants with long chain alkyl ammoniumheadgroups were synthesized, and their molecular structures were characterized by IR,1H-NMR, MS spectra and elemental analysis. The results proved that these surfactantswere objective products with high purity.(3) The surface activity and micellization properties of Gemini surfactantsCmCsCm(Cn)Br2were investigated by the surface tension, conductivity, steady-statefluorescence, dynamic light scattering (DLS) and transmission electron microscope (TEM) measurements. According to the study, with increasing the number of carbonatoms of alky chain of headgroup and tail chain, the surface activity and the tendencyto form aggregates increased, but the increase in the number of carbon atoms ofspacer produced the reverse consequences. The aggregation of these Geminisurfactants all reflected the enthalpy-entropy compensation effect. The Geminisurfactants CmCsCm(Cn)Br2can spontaneously self-assemble to form vesicles inaqueous solutions, and the vesicles formed by C12C4C12(C4)Br2can further cohere toform "string of pearls" like aggregates because of the hydrophobic interactions ofn-butyl chains of headgroups.(4) The surface activity and micellization properties of Gemini surfactantsCmC2ONC2NOC2Cm(C2)Cl2and CmC2OOC2OOC2Cm(C2)Cl2were studied by meansof surface tension, electrical conductivity, steady-state fluorescence probing, viscosity,DLS and TEM. The results showed the surface activities and the tendency to formaggregates increased with the increase in the tail lengths of Gemini surfactants. Thesurface tension of these Gemini surfactant solutions still decreased when theirconcentrations exceed the cmc, which was an unusual behavior. According to theGibbs adsorption theory, this unusual behavior could be attributed to the fast increaseof the counterion activity. The aggregation of these Gemini surfactants all reflectedthe enthalpy-entropy compensation effect. These Gemini surfactants with diamido ordiester spacer can spontaneously self-assemble to form vesicles in aqueous solutions,and the spongelike aggregates were observed in the solutions of CmC2ONC2NOC2Cm(C2)Cl2(m=10,12,14,16) at high concentrations. The salt-induced big aggregates(vesicles or spongelike aggregates) to small micelles transition might be caused by theextrusion of water from the double layer at high concentration of salt.(5) The corrosion inhibition and the adsorption of Gemini surfactantCmCsCm(Cn)Br2at aluminum/hydrochloric acid solution interface were studied bymeans of weight loss, hydrogen evolution and scanning electron microscopy. Theresults showed that CmCsCm(Cn)Br2were efficient inhibitors for aluminium corrosionin1M HCl solution, and they had strong capacity of adsorption. The adsorption ofCmCsCm(Cn)Br2at the aluminum/hydrochloric acid solution interface could beconsidered as a synergistic adsorption between CmCsCm(Cn)2+and counterion Brˉ.The inhibition efficiency and coverage of these surfactants increased with increasingthe number of carbon atoms of the tail chain, but decreased with the increase in thenumber of carbon atoms of head groups and spacer chain, which means the surfactant adsorbed layer on the aluminum surface became tighter with increasing the number ofcarbon atoms of the tails, but became looser with increasing the number of carbonatoms of the spacer and the alkyl chain of headgroup.The innovations of this work are as follows:(1) The control of the aggregation morphology transition (micelle to vesicletransition and vesicle to string of vesicle transition) was achieved by increasing thealkyl chain length of headgroups of the quaternary ammonium salt Geminisurfactants.(2) The mechanism of the temperature-induced vesicle aggregation anddispersion in the aqueous solution of C12C4C12(C4)Br2was proposed.(3) The unusual behavior of surface tension of Gemini surfactants aqueoussolutions were analyzed and explained.(4) The mechanism of the salt-induced vesicle and spongelike aggregate tomicelle transitions in the aqueous solution of Gemini surfactant CmC2ONC2NOC2Cm(C2)Cl2was proposed.(5) The synergistic adsorption model of Gemini surfactant C12C4C12(C4)Br2at thealuminum/hydrochloric acid solution interface was proposed.
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