Film from

A quite different means for the experimental determination of surface excess quantities is ellipsometry. The technique is discussed in Section IV-3D, and it is sufficient to note here that the method allows the calculation of the thickness of an adsorbed film from the ellipticity produced in light reflected from the film covered surface. If this thickness, t, is known, F may be calculated from the relationship F = t/V, where V is the molecular volume. This last may be estimated either from molecular models or from the bulk liquid density. 

Film pressure is often measured directly by means of a film balance. The principle of the method involves the direct measurement of the horizontal force on a float separating the film from clean solvent surface. The film balance has been considerably refined since the crude model used by Langmuir and in many... 

A. Ulman, An Introduction to Ultrathin Organic Films From Langmuir-Blodgett to Self-Assembly, Academic, New York, 1991. 

In an interesting medical application, the formation of a stable black foam film from amniotic fluid can be used as an assessment of fetal lung maturity [206]. 

The transfer of Langmuir films from the air-liquid surface to a solid substrate has come to be known as Langmuir-Blodgett deposition, after its developers [130, 131]. The solid substrates are usually hydrophilic surfaces such as... 

Chemical properties of deposited monolayers have been studied in various ways. The degree of ionization of a substituted coumarin film deposited on quartz was determined as a function of the pH of a solution in contact with the film, from which comparison with Gouy-Chapman theory (see Section V-2) could be made [151]. Several studies have been made of the UV-induced polymerization of monolayers (as well as of multilayers) of diacetylene amphiphiles (see Refs. 168, 169). Excitation energy transfer has been observed in a mixed monolayer of donor and acceptor molecules in stearic acid [170]. Electrical properties have been of interest, particularly the possibility that a suitably asymmetric film might be a unidirectional conductor, that is, a rectifier (see Refs. 171, 172). Optical properties of interest include the ability to make planar optical waveguides of thick LB films [173, 174]. 

Adsorbents such as some silica gels and types of carbons and zeolites have pores of the order of molecular dimensions, that is, from several up to 10-15 A in diameter. Adsorption in such pores is not readily treated as a capillary condensation phenomenon—in fact, there is typically no hysteresis loop. What happens physically is that as multilayer adsorption develops, the pore becomes filled by a meeting of the adsorbed films from opposing walls. Pores showing this type of adsorption behavior have come to be called micropores—a conventional definition is that micropore diameters are of width not exceeding 20 A (larger pores are called mesopores), see Ref. 221a. 

Neither the thermodynamic nor the rheological description of surface mobility has been very useful in the case of chemisorbed films. From the experimental point of view, the first is complicated by the many factors that can affect adsorption entropies and the latter by the lack of any methodology. 

Another approach to the fabrication of LB films from prefonned polymers is to fonn a hydrophobic main chain by reacting monomers tenninated by a vinyl group [102, 103, 104, 105 and 106]. The side groups studied also included perfluorinated hydrocarbon chains, which tilt with respect to the nonnal to the plane of the film, whereas the analogous ordinary hydrocarbon chains do not [105]. 

Riohard J, Barruad A, Vandevyver M and Ruaudel-Teixier A 1988 A 2-step transfer of oonduoting Langmuir films from a glyoerol subphase Thin Solid Films 159 207-14... 

Penner T L, Schiidkraut J S, Ringsdorf H and Schuster A 1991 Oriented films from polymeric amphiphiles with mesogenic groups—Langmuir-Blodgett liquid-crystals/Macromo/ecu/es 24 1041-9... 

Sauer T, Arndt T, Batchelder D, Kalachev A A and Wegner G 1990 The structure of Langmuir-Blodgett-films from substituted phthalocyaninato-polysiloxanes Thin Solid Films 187 357-74... 

Erosion is the deterioration of a surface by the abrasive action of solid particles in a liquid or gas, gas bubbles in a liquid, liquid droplets in a gas or due to (local) high-flow velocities. This type of attack is often accompanied by corrosion (erosion-corrosion). The most significant effect of a joint action of erosion and corrosion is the constant removal of protective films from a metal s surface. This can also be caused by liquid movement at high velocities, and will be particularly prone to occur if the solution contains solid particles that have an abrasive action. 

Numerous teclmiques have been developed for depositing films from vapours, ranging from straightforward evaporation to advanced chemical transport in which reactions are activated by heat, light or plasma. These have been surveyed in two comprehensive reviews [8, 9] and two popular interdisciplinary textbooks [K), H]. The tliree most widely used chemically based teclmiques are ... 

Calendering. The rheological characteristics of the sheet extmsioa grades of ABS easily adapt them to caleaderiag to produce film from 0.12... 

Linear Low Density Polyethylene. Films from linear low density polyethylene (LLDPE) resias have 75% higher tensile strength, 50% higher elongation-to-break strength, and a slightly higher but broader heat-seal initiation temperature than do films from LDPE. Impact and puncture resistance are also improved over LDPE. Water-vapor and gas-permeation properties are similar to those of LDPE films. 

The gate-roU size press is used for the appHcation of high soHds, high viscosity compositions to the surface of the sheet (92). The material to be appHed is transferred over a series of roUs, and a thin film from the appHcator roU is appHed to the sheet. 

Films from prepolymer solutions can be cured by heating at 150°C. Heating the prepolymer in molds gives clear, insoluble moldings (38). The bulk polymerisation of DAP at 80°C has been studied (35). In conversions to ca 25% soluble prepolymer, rates were nearly linear with time and concentrations of bensoyl peroxide. A higher initiator concentration is required than in typical vinyl-type polymerisations. 

Inorganic monomers can be used to plasma-deposit polymer-type films (16). At high plasma energies, the monomers are largely decomposed and can be used to form materials such as amorphous hydrogen-containing siUcon films from SiH for thin-film solar-ceU materials. 

AH the difficulties ia achieving dark colors for PVC siding apply also to door and wiadow frames and sashes. Coextmsion of a PVC core capped with a vinyl or acryUc film from an adjacent extmder can be used. In addition, PVC-acryUc alloys can be used for dark colors. The modifiers, stabilizers, and pigments iacorporated ia siding are used ia these products as well. To date, hiiilding codes restrict their use ia aew coastmctioa, so that their iastaHatioa is primarily as replacemeats. 

PZN-PT, and YBa2Cug02 g. For the preparation of PZT thin films, the most frequently used precursors have been lead acetate and 2irconium and titanium alkoxides, especially the propoxides. Short-chain alcohols, such as methanol and propanol, have been used most often as solvents, although there have been several successful investigations of the preparation of PZT films from the methoxyethanol solvent system. The use of acetic acid as a solvent and chemical modifier has also been reported. Whereas PZT thin films with exceUent ferroelectric properties have been prepared by sol-gel deposition, there has been relatively Httle effort directed toward understanding solution chemistry effects on thin-film properties. 

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