Thin polymeric

Membrane A thin polymeric film with pores. 

Thin polymeric films have important industrial apphcations (e.g., as protective coatings, lubricants, adhesives, dielectric or nonlinear optic devices, etc.) and pose many fundamental problems of film stability [1,2,4]. An important question, therefore, is whether these films break up and spontaneously dewett the substrate, resulting in the formation of droplets. The... 

Finally, it has been reported that carbon electrodes modified with thin polymeric films of polypyridyl metal complexes containing a dispersion of metal particles (Rh° or Pd°) can be used as electrocatalyst for reduction of C02 to hydrocarbons in MeCN. Apparently CH4 is the dominant reduction product (up to 18% of faradaic efficiency).123,124 It should be noted that the product distribution is reminiscent of a Fischer-Tropsch process since C2, C3, and C4 hydrocarbons are also formed. 

E. Wang, M.E. Meyerhoff and V.C. Yang, Optical detection of macromo-lecular heparin via selective coextraction into thin polymeric films, Anal. Chem., 67 (1995) 522-527. 

I.H.A. Badr and M.E. Meyerhoff, Highly selective optical fluoride ion sensor with submicromolar detection limit based on aluminum(III) octaethylporphyrin in thin polymeric film, J. Am. Chem. Sac., 127(15) (2005) 5318-5319. 

Thin Polymeric Films with Fluorescence Probes. Makromol. Chem. 192, 1981-1991. Balter, A. (1997) Probing Bioviscosity via Fluorescence, J. Fluorescence 7, S99—105. Bokobza L. (1990) Investigation of Local Dynamics of Polymer Chains in the Bulk by... 

D. Anwand, F. W. Muller, B. Strehmel, and K. Schiller, Determination of the molecular mobility and the free volume of thin polymeric films with fluorescence probes, Makromol. Chem. 192, 1981-1991 (1991). 

Electrodes coated with thin polymeric films of poly-c -[Ru(vbpy)2(H20)2] " (vbpy = 4-methyl-4 -vinyl-2,2 -bipyridine) or poly-cw-[Ru(pyr-bpy)2(H20)2] (pyr-bpy = 4-(2-pyrrol-l-yl-ethyl)-4 -methyl-2,2 -bipyridine) have been prepared, and cyclic voltammograms of these films are similar to that of c -[Ru (0)2(bpy)2] in solution. ... 

Membrane filters are usually made by casting a polymer solution on a surface and then gelling the liquid film slowly by exposing it to humid air. The size of the pores in the membranes can be varied by altering the composition of the casting solution or the gelation condition. Another common technique is to irradiate a thin polymeric film in a field of a-particles and then chemically etch the film to produce well-defined pores. 

Membranes are thin polymeric films that may permit the faster diffusion of some molecules than of others. Thin films of polymers are widely used for the separation of gases and for liquid-phase separations (dialysis). Because of the ease of property tuning, polyphosphazenes are of great interest for these types of applications, although only a few examples have yet been investigated. 

Electrostatic coating has been developed recently to allow for the deposition of thin polymeric films without the need for any solvent. Films are formed when a charged particle is attracted to a substrate of opposite charge.41 An example is the Accudep controlled release system.42... 

We report here on the structure and gas transport properties of asymmetric membranes created by the Langmuir-Blodgett deposition of ultra-thin polymeric lipid films on porous supports. Transmission and grazing angle FTIR spectroscopy provide a measure of the level of molecular order in the n-alkyl side-chains of the polymeric lipid. The level of orientational order was monitored as a function of the temperature. Gas permeation studies as a function of membrane temperature are correlated to the FTIR results. 

Fig. 7. Demonstration unit of a membrane module with a dense, thin polymeric membrane and polymeric microstructured support...

As temperature increases, the layer expands and the orientation of endbeads smears. This is shown in Figure 1.46. The observed expansion of layer thickness is attributed mainly to the temperature dependence of the intermolecular interaction and excluded volume effect not due to bond stretching. Temperature dependence, which is pertinent to the annealing process of thin polymeric lubricant films, has been carefully examined by Hsia et al. [171]. 

D. M. Phillips, A. S. Khair, and M. S. Jhon, Mathematical simulation of ultra-thin polymeric... 

S. Izumisawa, Q. Guo, and M. S. Jhon, The structural nonuniformity and molecular motion of molecularly thin polymeric film, (manuscript in preparation). 

The dye-loaded dendrimer 110 can be detected by means of single-molecule fluorescence.48,57,281,282 This multichromophoric system was embedded into a thin polymeric film at very low concentrations so that individual dendrimer molecules could be studied by far-field fluorescence microscopy at room temperature. Temporal fluorescence intensity fluctuations, fluorescence spectra, and decay times were measured separately or simultaneously. Collective on/off jumps of the fluorescence intensity as well as different emissive levels were observed for single dendrimer molecules with eight perylenemonoimide chromo-... 

The structure of polymer surfaces and thin polymeric films at the mesoscopic scale is of interest, both for application and basic research [1] As the size of many technological devices decreases, the natural length scales of many typical polymers such as the radius of gyration, the persistence length, or the domain size in block copolymers, match the feature size and thus the materials are expected to display a new behaviour [2-5], On the other hand, the tendency towards spontaneous structure forma-... 

The deposition of thin polymeric films from a cold plasma in a radio-frequency glow discharge apparatus has become an important means of modifying surfaces in materials applications [42], Applications receiving much attention recently have been the use of plasma polymerization to obtain biocompatible materials, and to produce functional surfaces for attachment of biologically active substances [43-45]. In this respect, many studies of protein adsorption have been... 

Controlled release formulations are a recent innovation in which the pesticide is incorporated into a carrier, generally a polymeric material (Scher, 1999). The rate of release of the pesticide is determined by the properties of the polymer itself as well as environmental factors. There are mainly two types of CR formulations reservoir devices and monolithic devices. As shown in Figure 2.1, in the reservoir device, the toxicant is enclosed in capsules of thin polymeric material to become microcapsules (1-100 pm in diameter), e.g., Penncap-M microcapsules (methyl parathion). In the monolithic device, the toxicant is uniformly... 

Fig 71 Assembly of Au-nanoparticles (5 nm) on thin polymeric films made from block copolymers via selective hydrogen-bonding units. Reprinted with permission from [240]... 

Accordii to these results the following important statement can be made the structure of oligomeric foams is a matrix system of thin polymeric films with two groups of cells, diarply differing in size and number and enclosed into one anotiier. 

These results reveal that- a plastic foam structure may be considered as a system of thin films and, therefore, support a model of plastic foam morphology namely a matrix system composed of thin polymeric films defining two groups of cells (macro- and microcells). Additional support in favor of this model of plastic foam structure is provided by the studies on the electric properties of plastic foams Among the numerous equations so far advanced for the calculation of the dielectric properties, the expressions which describe the dry foam structure by one of the limiting cases of a matrix system, namely a laminated dielectric structure with layers parallel to the force lines of the electrical field, agree best with the experiments >. 

Supported liquid membranes comprised the bulk of the published literature on the transport studies of metal ions across thin polymeric films [16,56-59]. Several literature reports on actinide transport across supported liquid membranes using various types of extractants viz., acidic extractants, neutral extractants and amine extractants are discussed below. 

FIGURE 43.7 Examples of porous structures produced in thin polymeric films using various methods of irradiation and chemical treatment. (Reprinted from Apel, P., Radial. Meas., 34, 559, 2001. With permission from Elsevier.) (A) Cross section of a polycarbonate membrane with cylindrical nonparallel pore channels (B) polypropylene membrane with slightly conical parallel pores (C) polyethylene terephthalate membrane with cigar-like pores and (D) polyethylene terephthalate membrane with bow-tie pores. 

Polymer nanoparticles with diameters of 50-500 nm are now widely used. As with microspheres and microcapsules, one can differentiate between solid polymeric spheres (nanoparticles) and those spheres with thin polymeric walls (nanocapsules). The locus of polymerisation is not an emulsion droplet as in microencapsulation, hut a micelle. The process involves the soluhilisation of a water-soluhle monomer such as acrylamide along with the dmg or other agent such as antigen to he encapsulated. An organic liquid such as n-hexane serves as the outer phase. Polymerisation is induced hy irradiation (y-rays. X-rays, UV light), exposure to visible light or heating with an initiator. 

An evanescent wave biosensor was devised for determination of analytes capable of intercalation in dsDNA in a FIA system. A polyethylene lensed optical fiber is coated with a thin polymeric layer containing dsDNA which is immobilized there. The fiber is placed in a FLA system immersed in a solution of ethidium bromide (144), which undergoes intercalation in the dsDNA. The fluorescence signal of 144 is thus enhanced about a 1000-fold relative to the evanescent wave fluorescence measurement without the coating and is dependent on the concentration in solution. If an analyte is present in the same solution, it competes with 144 for intercalation in the DNA and causes fluorescence quenching, which can be measured and correlated to the analyte concentration. This method was applied to determination of various analytes, including 4, 6-diamidino-2-phenylindole dihydrochloride (145)247. 

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