Study On Synthesis And Property Of Anionic Gemini Surfactants

The surfactant is a kind of substance with double affinity. By weak interactionssome ordered molecular combinations can be self-assembled, which have someimportant features. Surfactants have relatively high surface activity, which are widelyused in all aspects of industry and agriculture and daily life. Gemini surfactant is alsocalled as dimeric surfactants, which is a new type of surfactant with a special structure.Gemini surfactant is made of two traditional surfactants connected by a spacer groupcovalently. The special molecular structure will lead to some unique surface chemicalproperties and the Gemini surfactant is widely used in the field of washing andtertiary oil recovery industry. Its appearance has opened up new avenues for scientificresearch in the field of surfactants.In this research, five DADS surfactants were synthesized using diphenyl etherand bromoalkane as raw materials with alkylation-sulfonation-neutralization syntheticroute. Their structures were proved by IR, TG and Gel chromatography. Theoptimized methods of synthesis were determined by discussing the factors affectingreactions.The surface tension of the DADS surfactants were measured, we could draw thecritical micelle concentration and the surface tension at their CMC of the surfactant.The results showed that the surface tension at their CMC of the DADS geminisurfactant with different carbon chain is from32mN·m^-1to35mN·m^-1, the criticalmicelle concentration is from0.6mmol·L^-1to0.97mmol·L^-1.The surface tension of a series of DADS surfactants with different carbon chainwas measured, we obtained the critical micelle concentration and the surface tensionat their CMC of the surfactant. We found that as the carbon chain growth, the CMCbecome smaller, but because of the carbon chain of the C16-DADS is too long, thecarbon chain twisted in the solution surface and towards the air, it reduced theeffective hydrophobic chain on the gas-liquid interface, it caused the surface tensionincreases, therefore the surface tension at their CMC of the surfactant changesnon-linearly. Their CMC, γ_CMC, were measured, the results showed that DADS exhibits verygood surface activity and efficiency in reducing surface tension of water.