Templating Effects of Stearate Monolayer on Formation of Mg−Al-Hydrotalcite

The effect of a floating stearate monolayer on the formation of Mg−Al-hydrotalcite (Mg−Al-LDH) has been studied. A subphase was an aqueous solution of Mg(NO3)2·6H2O (1.6 × 10-3 M) and Al(NO3)3·6H2O (5.3 × 10-4 M) adjusted at pH = 10.5 by 1.0 M NaOH. Templating effects were studied in the following two ways. First, we spread a chloroform solution of stearic acid onto the above subphase and waited 6 h at zero surface pressure (0.51 nm2 molecule-1). After the surface was compressed to 20 mN m-1 (0.26 nm2 molecule-1), the floating film was deposited onto mica as a Z-type film (method 1). Second, we spread the same chloroform solution onto the subphase and started to compress the surface to the molecular area (0.40−0.20 nm2 molecule-1) after 30 min. The floating film was maintained at the constant surface pressure for 6 h. Thereafter, it was deposited onto mica as a Z-type film (method 2). From the atomic force microscope (AFM) images of the films, it was concluded that the largest thin crystals (ca. 3 × 10 μm...