Matsson Maria K, Kronberg Bengt, Claesson Per M
YKI, Institute for Surface Chemistry, Box 5607, SE-114 86 Stockholm, Sweden.
Langmuir. 2004 May 11;20(10):4051-8. doi: 10.1021/la035959p.
The equilibrium adsorption behavior of two n-alkyl-beta-D-glucosides (octyl (C8G1) and decyl (C10G1)) and four n-alkyl-beta-D-maltosides (octyl (C8G2), decyl (C10G2), dodecyl (C12G2), and tetradecyl (C14G2)) from aqueous solution on a titania surface, as measured by ellipsometry, has been investigated. The main focus has been on the effect of changes in the alkyl chain length and headgroup polymerization, but a comparison with their adsorption on the silica/water and air/water interfaces is also presented. Some comparison with the corresponding adsorption of ethylene oxide surfactants, in particular C10E6 and C12E6, is given as well. For all alkyl polyglucosides, the maximum adsorbed amount on titania is reached slightly below the critical micelle concentration (cmc), where it levels off to a plateau and the amount adsorbed corresponds roughly to a bilayer. However, there is no evidence that this is the actual conformation of the surfactant assemblies on the surface, but the surfactants could also be arranged in a micellar network. On hydrophilic silica, the adsorbed amount is a magnitude lower than on titania, corresponding roughly to a layer of surfactants lying flat on the surface. A change in the alkyl chain length does not result in any change in the plateau molar adsorbed amount at equilibrium; however, the isotherm slope for the alkyl maltosides increases with increasing chain length. Headgroup polymerization on the other hand affects the adsorbed amount. The alkyl glucosides start adsorbing at lower bulk concentrations than the maltosides and equilibrate at higher adsorbed amounts above the cmc. When compared with the ethylene oxide (EO) surfactants, it is confirmed that the EO surfactants hardly adsorb on titania, since the measured changes in the ellipsometric angles are within the noise level. They do, however, adsorb strongly on silica.
通过椭偏仪测量，研究了两种正烷基-β-D-葡萄糖苷（辛基（C8G1）和癸基（C10G1））以及四种正烷基-β-D-麦芽糖苷（辛基（C8G2）、癸基（C10G2）、十二烷基（C12G2）和十四烷基（C14G2））从水溶液在二氧化钛表面的平衡吸附行为。主要关注点是烷基链长度和头基聚合度变化的影响，但也给出了它们在二氧化硅/水和空气/水界面吸附情况的比较。还与环氧乙烷表面活性剂，特别是C10E6和C12E6的相应吸附情况进行了一些比较。对于所有烷基多苷，在二氧化钛上的最大吸附量在略低于临界胶束浓度（cmc）时达到，此时吸附量趋于平稳并达到一个平台期，吸附量大致对应于一个双层。然而，没有证据表明这就是表面活性剂聚集体的实际构象，表面活性剂也可能以胶束网络形式排列。在亲水性二氧化硅上，吸附量比在二氧化钛上低一个数量级，大致对应于一层平躺于表面的表面活性剂。烷基链长度的变化不会导致平衡时平台期摩尔吸附量的任何变化；然而，烷基麦芽糖苷的等温线斜率随链长增加而增大。另一方面，头基聚合度会影响吸附量。烷基葡萄糖苷比麦芽糖苷在更低的本体浓度下开始吸附，并在高于cmc时以更高的吸附量达到平衡。与环氧乙烷（EO）表面活性剂相比，证实EO表面活性剂在二氧化钛上几乎不吸附，因为椭偏角的测量变化在噪声水平范围内。然而，它们在二氧化硅上有强烈吸附。
