Study On The Mixed Systems Of Asymmetry Gemini Surfactants And Sodium Dodecyl Sulfate

It is well known that an unsymmetrical geometry Gemini surfactants may giveinteresting characteristics than symmetrical Geminis because of the more regulatory factors inthe molecular structure.The psysicochemical properties and adsorption mechanism of thethree asymmetry gemini surfactants and SDS mixed systems have been studied on the basis ofstatic/dynamic surface tension in this paper.Synergistic effects in mixed binary surfactant systems at different temperatures（25℃,30℃,35℃,40℃） have been investigated by calculating their surface chemical parametersobtained from the plots of γ^logC. The experimental results showed that XSOHC6, XSOHC8and XSOHEC8mixed with SDS respectively in binary systems exhibit improvedperformance，and the three complex systems（except XSOHC8/SDS,30℃, α=0.1） hadsynergistic effect in the formation of complex micelles under the temperature and ratiostudied. More synergistic interaction in surface tension effectiveness was observed inXSOHC8/SDS as compared to XSOHC6/SDS, also XSOHEC8/SDS exihibited synergistic inthis only at25℃and30℃. The measured cmc of mixed systems is decreased at begins andincreased latter with increased degree of dissymmetry gemini surfactant at the sametemperature.The synergism of XSOHC8/SDS having longer linear alkyl chain was strongerthan XSOHC6/SDS and XSOHEC8/SDS which hydrocarbon chains were branched.The dynamic surface tension measurements were performed to investigate air/wateradsorption macnanisms at concentrations（0.5cmc,5cmc,10cmc） for the mixed systems（XSOHC6/SDS, XSOHC8/SDS, XSOHEC8/SDS） at25℃by Pendant Drop Method andanalyzed in terms of asymptotic solutions to the Ward-Tordai equation. The resultdemonstrated that the DST plots of the mixed systems appear to be reverse S shape at lower concentration. And the adsorption rate becomes fast with the increase of concentration, thelower the concentration is, the longer induction region is. The result indicated that when theconcentration is above cmc, the initial adsorption is essentially diffusion-controlled, however,colse to equilibrium, the DST decay deviated from diffusion-controlled adsorption mechanismas compared to the model mixture. The effect of the concentration of the mixed systems onDST is more significant than the ratio of Gemini surfactant. When the hydrophilic group werethe same, adsorption barrier increaed and R_1/2 decreased as the hydrophobic becomed stronger,so was the dynamic surface activity. At low concentrations, XSOHC8/SDS mixed systemshad higher dynamic surface activety than XSOHEC8/SDS.