Wettability, Surface Morphology, and Stability of Long-Chain Ester Multilayers Obtained by Different Langmuir-Blodgett Deposition Types

Abstract

Methyl arachidate Langmuir-Blodgett multilayers, built up by X-, XY-and Y-type transfers, are characterized by means of contact angle measurements, and optical and atomic force microscopy under ambient conditions. Contact angle investigation shows identically high hydrophobicity of the surfaces produced by X-and Y-type depositions, implying molecular overturning during the X-type transfer. This overturning has not been detected in the previous X-ray study of small numbers of deposited fatty acid methyl ester monolayers. Molecular resolution AFM images of thin methyl arachidate LB films show a disordered surface structure. Scanning over larger film regions reveals a considerable difference in the surface morphology, corresponding to pure and mixed-type LB transfers. Reorganization of the multilayers occurs under ambient conditions in both cases. Larger aggregates, steps, and irregular islands are found with Y-type deposition. Ester LB films studied in an aqueous environment rearrange more easily than those stored in air. AFM imaging of the "contact line corrosion" of the multilayers shows a collective depletion of the whole LB film from the substrate at the wetting perimeter. The instability of the ester mono-and multilayers is explained on the basis of the intra-and interlayer molecular interactions within the spread and the deposited films, and by their weak adhesion to the substrate,

Photoelectrochemistry of Langmuir−Blodgett Films of Carotenoid Pigments on ITO Electrodes

“…22 Therefore, molecules deposited so as to form X films must rearrange during or shortly after deposition, so that the Y-structure is produced. 23 In the case of ACC it appears that the Y-type layered structure forms from the Z-type deposition procedure.…”

Self-assembly of alkyl chains of fatty acids in papermaking systems: A review of related pitch issues, hydrophobic sizing, and pH effects

“…Figure 14 provides a schematic definition of what is meant here by the term "overturn". Evidence of molecular overturn was obtained by Angelova et al (1994), who prepared Langmuir-Blodgett multilayers from long-chain fatty esters. Surprisingly, contact angle experiments yielded essentially the same results irrespective of whether the outermost molecular layer was inward-facing or out-ward facing.…”

“…Goddard and Ackill 1963;Binks 1991 Fatty acids within natural samples of wood and related bioresources are invariably mixtures, containing a range of unsaturated (such as oleic, linoleic, and linolenic acids) and saturated (such as stearic acid) components, in addition to triglyceride fats and other hydrophobic compounds such as -sitosterol (pine oil). Studies have shown that when such mixtures are collected as monolayer films, some of the component compounds may become self-segregated into separate domains (Angelova et al 1994;Lieckfeldt et al 1994;Johann et al 2001;Ocko et al 2002; Torrent-Burgués 2018).…”

“…The cited authors suggested that the relatively brittle nature of fatty acid soap films stabilized by the presence of divalent ions or aluminum ions can favor crumpling of the material, leading to the formation of a tacky, insoluble, macroscopic deposit. Indeed, work by Angelova et al (1994) showed a highly hydrophobic nature of such multilayers. The mechanism shown in Fig.…”

Maximum withdrawal speed for Langmuir–Blodgett film deposition of arachidic acid

“…The results showed that these divalent cations dramatically increased the film stability during the deposition. It has been observed that the transfer of Langmuir film from the gas-liquid interface onto a solid substrate is dependent on the characteristics of the sub-phase, solid substrate and deposition speed [12][13][14][15]. Previous studies [16][17][18][19][20][21][22][23] have revealed that divalent ions interact with arachidic acid (AA) and stearic acid (SA) in each layer to form "di-soap," which could enhance film stability.…”