Retracted films

In summary, mixed films of solute and solvent can be prepared as retracted films however, these are always transient or metastable systems, the probability of whose formation becomes greater the more fully does molecular adlineation of solute and solvent occur. If the concentration of polar solute is high enough, the film eventually becomes free of solvent as adsorption equilibrium is approached, and the retracted film is then free of solvent molecules. Where the solute and solvent molecules are so different in shape or size that the intermolec-ular cohesion between them through London dispersion forces becomes a minor factor, mixed films are never formed. Therefore, mixed films occur by the retraction process imder special conditions nonetheless, when they can be produced, a useful technique is available for studying the intermolecular interaction of solute and solvent molecules in the adsorbed state. 

One-Step Cameras and Processors. The eadiest one-step cameras used roU film and completed processing inside a dark chamber within the camera (9). The first instant color film, Polacolor, was provided in roU film format to fit these cameras. Flat-pack film cameras (Fig. 2), introduced in 1963, permitted the film to be drawn between processing rollers and out of the camera before processing was completed (10). Film holders for instant 10 X 13 cm (4x5 in.) film packets contain retractable rollers that permit the film to be loaded without mpturing the pod (11). For 20 x 25 cm (8 x 10 in.) films, the processing rollers are part of a tabletop processor. The exposed film, contained in a protective black envelope, and a positive sheet with pod attached are inserted into separate slots of a tray that leads into the processor. The film passes through the rollers into a covered compartment within which processing is completed. 

The film thickness and retractive index were calculated using spectroscopic ellipsometry. X-ray photoelectron spectroscopy (XPS) was used for composition analysis. Auger electron spectroscopy (AES) and secondary ion mass spectroscopy (SIMS) was used to investigate the depth profiles of the film. 

We demonstrated how ordered lines of colloidal polystyrene particles can be achieved by a simple dip coating process [70], We used wrinkles produced via a stretch retraction process of a glassy polyelectrolyte multilayer film mounted on a PDMS substrate. Here, the template was dipped into a colloidal particle suspension with the orientation of the wrinkle s grooves with the withdrawing direction of dipping as the sketch in Fig. 11 indicates. 

The final state of the interface is now just unfavaourable for spreading. This causes the initial spreading to be stopped, and can even result in the film retracting slightly to form very flat lenses, the rest of the water surface being covered by a monolayer of benzene. 

Further studies were done on rat embryonic fibroblasts (REFs) to identify how cell morphology and molecular composition of FAs are regulated by nanostruc-tured surfaces. In comparison to a gold thin film and a 58-nm-spaced pattern, cells cultured on 108-nm arrays display a delayed spreading followed by repeated protrusion-retraction cycles over several hours (Fig. 6b). The data suggest that cell... 

One method for hanging film in a shower is to use a retractable clothesline available from a home-building or variety store. Install the retractable line above the showerhead, and the receiving hook on the opposite wall. 

In collaboration with the University of Wageningen, magnetic resonance imaging (MRI) was used to visualize the film flow in the monoliths [15], As shown in Fig. 8.8, liquid (water) was fed onto a complete piece of monolith from which four channels then were prolonged for measurement. In Fig. 8.9, the liquid is represented as light areas in the corners of the four channels. Clearly, the channel walls are not uniformly irrigated. In the corners, the gas-liquid interface is shaped like an arc, whereas between the pockets, only a thin liquid film remains ( 70 pm). This retraction of the film into the corners can be attributed to the high surface tension of the liquid used (water). Additionally, the liquid pockets of one channel have different sizes, and this leads to channel scale maldistribution. 

A bare platinum electrode was coated with a close-packed monolayer of n-octadecylamine by retraction from the molten crystal compound (2). The contact angle of methylene iodide with the monolayer was 68° to 70°, which should be true if the film was close packed. This film-coated electrode was used with the FEP resin-covered gold electrode in the experimental sequence described... 

Adsorbed films of ethykriethoxysilane and vinyltriethoxy-silane were formed on silica and alumina by retraction from hydrocarbon solution and their wettabilities and water-stabilities determined. The vinyltriethoxysilane films were generally more oleophobic, more hydrophobic and more resistant to contact with water than the films formed by the ethyl analog. Neither adsorbate formed stable films on a-alumina. The addition of low molecular weight organic acids or bases to the adsorbate solution resulted in both the ethyl and vinyl compound forming hydrophobic and water-stable films on silica and ot-alumina. Films of p-chloro-phenyl-ft-ethyltrichloro, -trimethoxy, and -triethoxysilane were also studied and found to be water-stable and to have wettabilities characteristic of a surface comprised of closely-spaced p-chlorophenyl groups. 

The present paper describes the adsorption of ethyltriethoxysilane (ETES) and vinyltriethoxysilane (VTES) at various organic-liquid/silica interfaces. Films formed by these compounds on silica and glass from solution in nonpolar organic liquids were found to be oleophobic and so could be isolated by retraction that is, the substrate on which the films had been formed emerged dry from the solution, thus allowing direct examination of the adsorbed layer. 

Ethyltriethoxysilane (ETES). The critical surface tensions of the ETES films obtained on silica by retraction from 1% solutions in a-chloro-naphthalene are plotted in Figure 2A. The adsorption time—i.e., the abscissa—is the time the silica substrate was allowed to remain in contact with the adsorbate solution. Adsorption times longer than 20 hours did not produce any further decrease in yc and solutions containing 0.1% and 5% ETES gave values within 1 dyne/cm. of those in Figure 2A. Attempts to obtain ETES films from solution in isopropylbicyclohexyl were unsuccessful—the solutions did not retract from the test surfaces even after 20 hours adsorption time. Isopropylbicyclohexyl has a surface tension of 34.4 dynes/cm. so if the ETES adsorbed to form films having yc values of 33-35 dynes/cm., as it had from -chloronaphthalene, then the bicyclohexyl solution would not be expected to retract. 

ETES films could not be obtained on alumina substrates by retraction. Retraction did not occur from solutions of the triethoxysilane even up to concentrations of 5%, and adsorption times of many days. This was the case using both air-dried and flamed alumina and for a-chloro-naphthalene or isopropylbicyclohexyl as the solvent. 

VTES films could be obtained on a-alumina by retraction from VTES-(a)-chloronaphthalene solutions. This contrasts with the failure of ETES solutions to retract from a-alumina. However, neither the organic liquid or water would give stable contact angles on the films formed by VTES. 

If retraction was incomplete, the silica or alumina plates were subjected to the water desorption test, and it was consistently found that the water displaced the thin visible layer of adsorbate solution. This water treatment left the surface dry and free of visible film yc and 0H2o determinations were made on these washed surfaces (Table II). 

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