Stearic acid monolayer reflectivity

IR reflectance-absorption spectra (IRRAS) of Langmuir-Blodgett stearic acid and deuteriated stearic acid monolayers on gold and aluminium... 

The concept of ATR at the interface of two media is described in 1.4.10° and Section 1.8.3. In situ ATR measurements of ultrathin films started in the mid-1960s with studies of the adsorption of a stearic acid monolayer from D2O onto Ge [448], and chemical [449] and electrochemical [450] oxidation of Ge, where a Ge multiple internal reflection element (MIRE) acts as both the substrate and the electrode. Later, coated ATR [60, 451-454] and MO ATR with the SEIRA effect [455] were introduced in in situ experiments. The principal advantage of the ATR geometry is that the corresponding in situ cells are free from diffusion effects (the volume of solution phase in contact with the IRE is arbitrary), which is useful when studying time-dependent phenomena (Section 4.9.1). 

Figure 2. Ex-situ transmission FTIR results (a), in-situ near-normal external reflection FTIR results (b) on the mixed monolayers spread on aqueous cadmium solution (ImM, pH-S.S) with varying monolayer composition (stearic acid streayl alcohol), and the peak area of the asymmetric carboxylate band at various composition (c). The peak areas were normalized with respect to that of pure strearic acid case (100 0).

Figure 22. (A) The specular reflectivity of the calcite-water interface (squares), with similar data for a calcite surface in contact with a 5 mM solution of stearic acid in methanol (The calcite-water data are offset vertically by a factor of 10, for clarity). The measurements were performed in a transmission cell. The solid lines are best-fit structure factor calculations for selected models. The thick solid line through the stearate data is optimized for an extended stearate molecule adsoibed on top of the calcite surface, as shown in (B). The thin solid line through the stearate data is optimized for the carboxylic head group substituting for surface carbonate ions of the calcite lattice. (B) Best-fit model for the stearate monolayer adsorbed on calcite.

Reflection electron diffraction patterns from glass surfaces treated in hexadecane solutions of cerotic and stearic acids were obtained and compared with diffraction patterns taken by Bigelow [5] of monolayers of the same acids. The agreement was sufficient to conclude that the... 

However, how the morphology of the superhydrophobic PMMA surface was formed is still a question and needs to be explored further. As discussed above, after modification with ethylenediamine-anhydrous ethanol mixture for 3 h, the PMMA plates had a water CA of 55.9 0.9°, a value between the water CA values of pristine PMMA and NH2-terminated self-assembly monolayer. Therefore, we believe that the methyl ester functional groups on the surface of PMMA plates, when processed in ethylenediamine-anhydrous ethanol mixture, did not react with ethylenediamine completely and only a part of surface ester groups participated in aminolysis reaction. So, in the following reaction with stearic acid, stearic acid would anchor and crystallize preferably in the NH2-modified micro-region, which will induce the formation of flower-tike structures. The ATR spectra also indicate the same information. The spectra (a) and (b) in Fig. 6 are the attenuated total reflectance (ATR) infrared spectra of pure PMMA and NH2-modified PMMA, respectively. The major observations from comparison of spectra (a) and (b) are the presence of the amide I... 

Stearic acid adsorbed from heptane solution on to magnesium hydroxide (as magnesium stearate) was shown to exhibit structural order [49]. This was manifested as a reflection that became apparent at coverage levels at and beyond monolayer. The d-spacing of the reflection corresponded to the short spacing of magnesium stearate. Isostearic acid and oleic acid adsorbed under the same or similar conditions as the stearic acid showed no evidence of structural order due to the inability of the alkyl/alkenyl chains to pack into an ordered structure [13]. 

---