ABSTRACT
The aggregation of surfactant forms various structures, but the structures keep only in the solutions. AFM can observe the morphology of the aggregations in the solution as in in situ observation. Therefore, the observation can clarify the true morphology of the aggregation at the solid-liquid interface; in addition, it can observe the growth process of the aggregation in situ.
1. Heterogeneous Growth of Adsorption Film Figure 13 shows a typical sequence of AFM images observed everywhere of a mica surface at the various lapse of times after the introduction of 0.1-mM aqueous C18 TAB solution until the stable morphology is approached at 158 min. Figure 13a indicates the intact surface of mica observed in pure water. The range scanned was 2000 x 2000 nm. Figure 13b shows the (;mergence of numerous tiny islands of the diameter around 10--30 nm 6 min after the injection of the aqueous surfactant solution, which suggests the two-dimensional molecular aggregates of adsorbed surfactant. The image of Fig.13c, observed at 15 min, clearly shows that the small islands as observed in Fig. 13b grew into larger patches, which have a terrace structure. Figure 13d shows that the area of each island increased further with the elapse of time while the height of the island remained unchanged. Figure 13e--h show the occurrence of spontaneous fusion among those grown-up patches.
