Cast multibilayers

the type and concentrations) of the electrolytes bathing the BLM, the ions adsorbed on the BLM surface, and the extent to and frequency with which the BLM is bent [419]. These experimental observations have led to a phenomenological definition of the flexoelectric coefficient, f, as the ratio between the bending-induced transmembrane potential, Uf, and the change of curvature, c, that accompanies the bending of the membrane  

An evaluation of f requires electrical measurements of Uf, together with a knowledge of BLM deformation during its subjection to oscillating hydrostatic pressure. 

Flexoelectricity involves two degrees of freedom of the BLM electrical and mechanical. The system is amenable to simultaneous electrical and optical investigation of mechanical-to-electrical-energy conversion mediated by a bi-molecularly thin membrane. BLMs themselves are unlikely to be used as device components. They offer, however, an eminently suitable means for conducting the fundamental studies which are necessary for the full potential of the membrane-mimetic approach to advanced materials to be realized. 

Controlled evaporation of SUVs and MLVs on substrates has been shown to result in the formation of ultrathin films which retained the regular bilayer structure of vesicles [69, 425-427]. These immobilized bilayers, termed as cast multibilayers , cast multibilayers , or ordered cast (ultrathin) films , have provided an alternative to LB films [425-446]. Alkylammonium surfactants with azobenzene (33) and glutamate (34) functionalities have been used, for example, in the preparation of cast-film-forming SUVs. X-ray diffraction 

Cast multibilayers prepared from an azobenzene-containing surfactant (33) [426] and from mixtures of 33 and 5 display only short-term stabilities and low solubilities in water. These disadvantages have been overcome by coating the multibilayers with cellulose acetate and by using poly(vinyl alcohol) as a binder [429], The method of choice in preparing these composite cast multibilayers 

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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. 

Fig. 64. Plausible model of the molecular packing of the cast multibilayer of 34 as produced by electron-density matching of the X-ray diffraction data. The plane of the benzene ring is arbitrarily set in the plane of the two alkyl chains. When the benzene plane is assumed to be in the perpendicular disposition, the tilt angles for the spacer and tail chains become slightly greater 50° for the spacer and 75° for the tail [445]...

Fig. 65a, b. Photographs of cast multibilayer films a stiff 33 film b flexible 34 film [445]... 

Composite cast multibilayers provided a route to the formation of multilayer, two-dimensional polymer networks [443, 445]. This method utilized the following steps (i) ultrasonic dispersal of 15 mM of the dialkylammonium surfactant, 35, and 15 mM of the bisacrylate monomer. 36 (ii) addition of... 

Fig. 67. Schematic representation of three types of anionic porphyrins in a cast multibilayer film of 34. The overall bilayer organization is assumed to be the same as that of Fig. 64. For clarity, counterions are not shown and the bilayer units are separated from each other. The spacer portion is also not shown in Stereogram . Type I porphyrins (Fig. 66) are inserted into the bilayer along the molecular axis of the spacer chain. Type II porphyrins are randomly placed on the bilayer surface. Type III porphyrins lie flat on the bilayer [445]...

A similar approach has been taken for preparing molecularly controlled siloxane networks [440,446]. Composite bilayer films were cast from mixtures of alkoxysilane (CH3Si(OCH3)3) and 37 or 38 on a fluorocarbon sheet and were kept at 25 °C and 60% relative humidity for three days. Exposure to gaseous ammonia in a closed vessel for ten days resulted in hydrolysis and subsequent condensation. The surfactants were then extracted by repeated immersion in methanol. Manipulation of the composition of the cast multibilayers allowed... 

Myoglobins [442] and iron-oxide particles [447] have also been organized in cast multibilayers. Flexibility and versatility render composite cast multibilayers to be suitable for the construction of functional, ultrathin, polymeric superstructures with molecularly defined morphologies. Cast-multibilayer... 

Cast multibilayers 2D,3D depends on substrate dimensions Controlled evaporation of surfactant deposited on substrates Weeks Viable alternative to LB films 427... 

Cast multibilayers prepared from cyclam-containing double-chain surfactants Size-quantized CdS particles generated in situ in cast bilayers... 

Cast multibilayers prepared from N-(co-(trimethyl-ammonio)undecanoyl) dioctadecyl-L-glutamate bromide dispersions Fe304 particles generated in situ Magnetic anisotropy of particles was retained in cast multibilayer films 797... 

S. Asakuma, H. Okada, T. Kunitake, Template Synthesis of Two-Dimensional Network of Cross-Linked Acrylate Polymer in a Cast Multibilayer Film , J. Am. Chem. Soc., 113, 1749 (1991)... 

Nassar, A.-E., Z. Zhang, V. Chynwat, H.A. Frank, J.F. Rusling, and K. Suga (1995). Orientation of myoglobin in cast multibilayer membranes of amphiphilic molecules. J. Phys. Chem. 99,11013-11017. 

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