Langmuir-Blodgett monolayer multilayers

This approach may also be applied to racemic bilayers built up from homo-chiral Langmuir-Blodgett monolayers. By measuring the two-dimensional diffraction pattern from such a bilayer it is possible to deduce the molecular chirality of each of the two monolayers in the order they were inserted to construct the bilayer. This approach can be extended to multilayers. Thus, in principle, we close the circle started in Section IV-G-1. It is possible to assign the absolute configuration of chiral molecules in centrosymmetric crystals provided that one can construct the crystal (in this case the multilayer) by adding homochiral layers one by one. 

Monomolecular layers and LB-multilavers. Compound 21 exhibits amphiphilic properties. Spreading at the air-water interface leads to the formation of oriented monomolecular layers. The monolayer forms a solid condensed phase at 20 C with a collapse pressure near SOmN/m. It can easily be transferred onto various hydrophobic substrates such as CaF, ZnS, AgCl, Si, Ga or metal surfaces, and Langmuir-Blodgett-type multilayers (21> of variable thickness can be built up. These multilayers also exhibit a rapid reaction if exposed to UV- or y-irradiation. From an infrared spectroscopic study described recently (ll-JA) a 1,4-addition reaction is evident, as it also occurs in microcrystalline powders of 21- The solid state polymerization of 21 is schematically represented by Figure 14. 

Arndt T, Schouten A J, Schmidt G F and Wegner G (1991) Langmuir-Blodgett monolayers and multilayers of preformed poly(octadecyl methacrylate)s. 2. Structural studies by IR spectroscopy and small-angle X-ray scattering, Makromol Chem 192 2215-2229. 

Biddle M B, Lando J B, Ringsdorf H, Schmidt G and Schneider J 1988 Polymeric amphiphiles with hydrophilic main chain spacers—studies in monolayers and Langmuir-Blodgett multilayers Oollold Polymer Scl. 266 806-13... 

Geddes NJ, Sambles JR, Jarvis DJ, Parker WG, Sandman DJ (1992) The electrical properties of metal-sandwiched Langmuir-Blodgett multilayers and monolayers of a redox-active organic molecular compound. J Appl Phys 71 756-768... 

Fig. 9.1 A schematic illustration of surface coatings with their typical thickness ranging from angstroms to micrometers. Selected are monomolecular layers fabricated by the transfer of Langmuir-Blodgett (LB) films onto solid substrates (1) self-assembled monolayers (SAMs) (2) multilayers thereof (3) polymer-...

Surfactants provide several types of well-organized self-assembhes, which can be used to control the physical parameters of synthesized nanoparticles, such as size, geometry and stability within liquid media. Estabhshed surfactant assembles that are commonly employed for nanoparticie fabrication are aqueous micelles, reversed micelles, microemulsions, vesicles [15,16], polymerized vesicles, monolayers, deposited organized multilayers (Langmuir-Blodgett (LB) films) [17,18] and bilayer Upid membranes [19](Fig. 2). 

Thin films of materials play an important role in modern electronics. Langmuir-Blodgett films (Mort, 1980) are prepared from surface-active molecules that adsorb at the surface of an aqueous solution. The surface is gently compressed to produce a close-packed monolayer, which can be coated on appropriate substrates by dipping at constant surface pressure. The layers so produced are of a precise thickness, and repeated dipping gives multilayers. For example, diacetylenes and other polymerizable... 

Description of the different mimetic systems will be the starting point of the presentation (Sect. 2). Preparation and characterization of monolayers (Langmuir films), Langmuir-Blodgett (LB) films, self-assembled (SA) mono-layers and multilayers, aqueous micelles, reversed micelles, microemulsions, surfactant vesicles, polymerized vesicles, polymeric vesicles, tubules, rods and related SA structures, bilayer lipid membranes (BLMs), cast multibilayers, polymers, polymeric membranes, and other systems will be delineated in sufficient detail to enable the neophyte to utilize these systems. Ample references will be provided to primary and secondary sources. 

Monolayers and multilayers on solid substrates have come a long way since their initial preparation by Katherine Blodgett during the 1930s [133, 134], Deservedly termed as Langmuir-Blodgett (LB) films , they have flourished... 

VIGNETTE VII MOLECULAR MONOLAYERS AND MULTILAYERS Langmuir-Blodgett Films... 

FIG. 7.1 Deposition of multilayers using the Langmuir-Blodgett technique (a and b) monolayer deposition and (c and d) multilayer deposition. 

At the bulk level, molecular and polymeric materials also offer flexibility of fabrication in various forms such as crystals, films, fibers, as well as monolayer and multilayer Langmuir-Blodgett films. In addition, one can make composite structures to introduce multifunctionality at the bulk level. 

Monolayers can be transferred onto solid substrates by the Langmuir-Blodgett technique giving rise to mono- or multilayers which can even have thicknesses in the range of the wavelength of visible light. The multilayer quality often depends on the quality of the first monolayer transfer. 

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