Laboratory of Interfaces and Nanosize Systems, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary.
J Colloid Interface Sci. 2012 Aug 1;379(1):78-83. doi: 10.1016/j.jcis.2012.04.053. Epub 2012 Apr 27.
The adsorption isotherms of n-decyl-β-D-glucoside (β-C(10)G(1)) as well as various n-alkyl-β-D-maltosides (β-C(n)G(2)) with n=8, 10, 12 and 14 were determined from surface tension measurements. Based on the analysis of the adsorption isotherms, the total free energy change of adsorption was determined and a novel method was proposed to determine the maximum adsorbed amount of surfactant. It can be concluded that the driving force for adsorption first increases with increasing adsorbed amount of the sugar surfactants and then levels off in a plateau. This peculiar behaviour is interpreted as formation of a thin liquid-like alkane film of overlapping alkyl chains at the air/water interface once a certain adsorbed amount is exceeded. The driving force of adsorption depends on the alkyl chain length only and is not affected by the type of the head group. The hydrophobic contribution to the standard free energy change of adsorption was compared with the values of sodium alkylsulfate and alkyltrimethylammonium bromide surfactants. This comparison reveals that the hydrophobic driving force of adsorption is the largest for the sodium alkylsulfates, whereas it is the same for the sugar surfactants and the alkyltrimethylammonium bromides.
从表面张力测量中确定了正癸基-β-D-吡喃葡萄糖苷（β-C(10)G(1)）以及各种正烷基-β-D-麦芽糖苷（β-C(n)G(2)）（n=8、10、12 和 14）的吸附等温线。基于吸附等温线的分析，确定了吸附的总自由能变化，并提出了一种确定表面活性剂最大吸附量的新方法。可以得出结论，吸附的驱动力首先随糖表面活性剂吸附量的增加而增加，然后在一个平台上趋于平稳。这种特殊的行为被解释为一旦超过一定的吸附量，在空气/水界面处就会形成重叠烷基链的薄液态烷烃膜。吸附的驱动力仅取决于烷基链长度，不受头基类型的影响。将疏水作用对吸附标准自由能变化的贡献与烷基硫酸盐和烷基三甲基溴化铵表面活性剂的值进行了比较。这种比较表明，对于烷基硫酸盐，吸附的疏水驱动力最大，而对于糖表面活性剂和烷基三甲基溴化铵则相同。
