多支链烷基苯磺酸钠水溶液的表面性质

用自制的四种高纯度多支链烷基苯磺酸钠,研究了支链结构对其表面性质的影响.结果表明,随支链烷基碳数增加,临界胶束浓度降低,标准吸附自由能DGadӨ更负;但是,饱和吸附量Γmax却随支链烷基碳数增加而减小,且临界胶束浓度时的表面张力γcmc随吸附量减小而降低,表现出与一般表面活性剂不同的变化趋势.从多支链烷基苯磺酸钠的分子结构特点,解释了随支链烷基碳数增加Γmax和γcmc的变化规律,探讨了分子的独占面积(as)对Γmax及γcmc的影响.

Surface Properties of Sodium Branched-alkylbenzenesulfonates

The relationship of surface property and hydrophobic branched-chain structure was studied using four branched-alkylbenzenesulfonates with additional alkyl substituents synthesized by our laboratory. From the surface tension measurements in pure water and 0.171 mol·L－1 NaCl solutions, the following parameters were calculated: critical micelle concentration (cmc), the surface tension at the cmc (γcmc),surface excess at the cmc (Γmax),area per molecule at the cmc (Amin), pc20, and standard free energy of adsorption (DGadӨ).Lengthening the branched alkyl chain at the meta-position of sulfonic group,Γmax decreased while γcmc decreased; At the same time, cmc decreased, pc20 increased, and DGadӨ became more negative. These results indicated that the hard-disk areas of sodium branched-alkylbenzenesulfonate molecules (as) affected adsorption and surface tension.