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Surfactants have been widely used in oil exploration, mineral flotation, emulsion polymerization, textile dyeing, food processing, et al, due to the properties of reducing interfacial tension and forming micelles in the solution. Most of occasions, surfactants are needed in just one step and have to be removed when it’s unnecessary. Sometimes, it is neither easy to remove the normal surfactant nor easy to recycle it after its devotion. And, the direct outpouring of surfactants is wasteful and environmentally harmful. Fortunately, switchable surfactants could address these problems by switching the surface activity. Being mildness and non-toxic, the CO2/Air switchable surfactant gains more attentions.In this subject, N’-alkyl-N, N-dimethyl ethylamidine has been synthesized in two ways. One is by acetal and fatty amines, and the other is by amino chloride and amide. It was found that the first way is hard in preparing and preserving the acetal in despite of higher yield. So, more experiments on the second way have been done to analyze the reaction mechanism and effect factors. As a result, the temperature and the reaction time can both influence the second way of synthesis, and the best reaction condition is reacting in 110℃for 20h.The surface activities of the CO2/Air switchable surfactant has been studied. According to the properties, the micelles from the N’-dodecyl-N, N-dimethyl acetamidine bicarbonate, 1-propanol, water, CS2 and the reversed micelles from N’-hexadecyl-N, N-dimethyl acetamidine bicarbonate, n-hexyl alcohol, n-heptane, water were made. Using these self-assembly micelles and reversed micelles, CdS nanometer quantum dots have been synthesized. The nanoparticles were then characterized by TEM, HRTEM, XRD, UV-vis and fluorescence. The result proved that the soft template of CO2/Air switchable surfactants could synthesis CdS nanometer quantum dots smaller than 10nm.In the post-processing stage, the CO2/Air switchable surfactants were verified switchable and recyclable.The amidine surfactants could be deprotonated and returned to the organic phase. This approach allowed easily breaking of micelles. And the alkyl amidines could be easliy removed from the nanoparticles. The alkyl amidines become watersoluble upon addition of CO2. This process could be used to resolve the seperation and recycle problems in micelles. Therefor, it could be wildly used in nanoparticle synthesis.
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