Li B, Fujii M, Fukada K, Kato T, Seimiya T
Faculty of Science, Tokyo Metropolitan University, 1-1 Minami-Oosawa, Hachioji, 192-03, Japan
J Colloid Interface Sci. 1999 Jan 1;209(1):25-30. doi: 10.1006/jcis.1998.5869.
The nature of adsorbed cationic amphiphiles at the mica/solution interface was studied by XPS and contact angle measurements. The elemental analyses of freshly cleaved mica surfaces by XPS showed that the potassium atoms on the surface lattice of mica are not necessarily distributed equally to each surface on cleavage. The adsorbed cationic amphiphile molecules remaining on mica surfaces after rinsing with distilled water were found to be anchored to the surface by ion-exchange, replacing surface potassium and/or other cations. The ratio of adsorbed cationic amphiphile molecules with single alkyl chains to the maximum potassium ions on mica surface was estimated to be twice as large as that of amphiphiles having two alkyl chains. The contact angle of water drops placed on the adsorbed surface showed a gradual decrease with the elapse of time due to the dissolution of adsorbed surfactant into the water drop; however, the decrease was not observed for those mica surfaces when aged for more than 3 days in the adsorption bath. The anchoring of adsorbed molecules by ion-exchange was found to occur extremely slowly, however; the anchored molecules may not easily be desorbed when rinsed with deionized water. The time dependent anchoring of adsorbed molecules was studied in terms of adsorption time, alkyl chain length, and concentration of cationic surfactant. Copyright 1999 Academic Press.
通过X射线光电子能谱（XPS）和接触角测量研究了云母/溶液界面处吸附的阳离子两亲物的性质。用XPS对新劈开的云母表面进行元素分析表明，云母表面晶格上的钾原子在劈开时不一定均匀分布在每个表面上。发现用蒸馏水冲洗后残留在云母表面的吸附阳离子两亲物分子通过离子交换锚定在表面，取代了表面钾和/或其他阳离子。估计单烷基链吸附阳离子两亲物分子与云母表面最大钾离子的比例是具有两条烷基链两亲物的两倍。由于吸附的表面活性剂溶解到水滴中，放置在吸附表面上的水滴的接触角随时间逐渐减小；然而，在吸附浴中老化超过3天的云母表面未观察到这种减小。然而，发现通过离子交换吸附分子的锚定极其缓慢；用去离子水冲洗时，锚定的分子可能不容易解吸。根据吸附时间、烷基链长度和阳离子表面活性剂浓度研究了吸附分子随时间的锚定情况。版权所有1999年学术出版社。
