Radiofrequency polymers

Baudoin etal. [168,169] first presented qualitative depth profiles of lacquer and polymer coatings by means of r.f. GD-OES. Quantitative depth profiles were successively obtained by Payling et al. [170] on prepainted metal coated steel. Samples comprised a (rutile) pigmented silicone-modified polyester topcoat over a polymer primer, on top of an aluminium-zinc-silicon alloy coated steel substrate. With GD-OES in r.f. mode, it was possible to determine the depth profile through the polymer topcoat, polymer primer coat, metal alloy coating, and alloy layer binding to the steel substrate with a total depth of 50 im, all in about 60 min on the one sample. GD-OES depth profiles of unexposed and weathered silicone-modified polyesters were also reported [171]. Radiofrequency GD-OES has further been used to... 

Each microreactor consists of a polymer-bound substrate and a radiofrequency encoded microchip enclosed within a small porous vessel. The radiofrequency tag allows the identity of the substrate contained within each microreactor to be established readily. Using this technology, the polymer-bound substrates 86 were individually elaborated, within separate microreactors, by sequential reactions with acids 87 and alcohols 88 in a similar way to the solution-phase processes [25c]. Each of the microreactors was then subjected to the tandem RCM resin-cleavage conditions employing initiator 3. The products from each microreactor were obtained as a mixture of four compounds (89-92). The library of analogs prepared by this technique was then screened for biological activity [25c]. 

Polypropylene (PP) is a hydrophobic and chemically inert polymer which needs to be activated in order to be functional as a support for NA immobilization. Typically, PP membranes are aminated by exposure to an ammonia plasma generated by radiofrequency plasma discharge. Once aminated, the PP membranes can be reacted with derivatized ONDs using common coupling methods [56-58]. 

Modifications of polymer surfaces by exposure to electrical plasmas and discharges have also been subjected to XPS examination in several recent articles (4, , 7). An example is the plasma oxidation of polyethylene, polypropylene and polystyrene in a radiofrequency inductively coupled system ( ). Figure 14 shows the Cls and 01s spectra of a polyethylene film after... 

Shick C. R. Jr., De Palma P. A. Jr. and Marcus R. K. (1996) Radiofrequency glow discharge mass spectrometry for the characterization of bulk polymers, Anal Chem 68 2113-2121. 

Radiofrequency tags encapsulated in grafted functionalized polymers have recently been reported (53), as have laser optical-encoded ceramics with grafted polystyrene supports (54). These devices have the properties of really big beads that contain the identifying tag and thus combine the features of chemically encoded libraries with the advantages of mechanically encoded libraries. 

The availability of pulsed field gradient (PEG) techniques has had the most significant impact in terms of making it possible to perform 2D- and 3D-NMR experiments on polymer samples. These methods have taken the place of traditional radiofrequency phase cycling methods for coherence selection. By optimizing the use of the spectrometer s dynamic range, PEG techniques not only save time but also drastically reduce artifact noise. 

The desired thickness of the film for the solar sail application was 2.5 ym, but the thinnest commercially available film of this type was Du Font s Kapton O) with a thickness of <7.5 ym. Hence, a need existed to thin the latter film and to assess the photo-and thermal stability of the resulting, thinned film. This paper describes the use of a radiofrequency (RF) oxygen plasma for etching (thinning) of poly[, N-oxydiphenylene) pyromellitimide] (POP) film, and presents data on the photo/thermal degradation of etched and unetched film in vacuum. Although plasma etching has been applied to many polymers, it has scarcely been used on... 

Busch, K.W. et al.. Residual changes in the surface charge of TiO2 (anatase) suspensions as a result of exposure to a 44 MHz radiofrequency electric field. Colloid Polym. Sci., 273, 1186. 1995. 

We have been concerned with the precision and accuracy of NMR data of polymers since we first started NMR studies on polymers.1-4 Using continuous-wave (CW) spectrometers, the effects of measurement conditions including temperature, sample concentration and radiofrequency (rf) field strength, were examined using several polymer and copolymer samples. Since our research group have been deeply involved in stereospecific polymerization of methacrylates, one of the main concerns about NMR measurement was the precision of tacticity determination by NMR. The errors in determining the tacticity of poly(methyl methacrylate) (PMMA) and those in the results of polymerization of methyl methacrylate (MMA) by radical and anionic initiators were examined and found to be satisfactorily small.4 Although there... 

Mechanism. The available evidence is thus not consistent with the generally proposed mechanism of polymer formation based on the random build-up of a poly(phenylene) chain accompanied by hydrogenation (4) or the interaction with the hexatrienyl diradical (18). In the radiofrequency discharge of benzene (21), evidence was presented which indicated that the polymer contained consecutive para linkages suggesting poly(p-phenylenes). Schuler (20) observed that the polymer (C/H 1.03, M.W. 503) was a phenyl substituted aliphatic chain based on infrared evidence. Patrick and Burton have demonstrated that hydrogen atoms are not involved to any significant extent in polymer formation when liquid benzene is irradiated with a 1.5 Mev. source (18). 

The work described here is an attempt to systematize the study of benzene reactions in radiofrequency discharges. The only products isolated in these reactions were diphenyl, a liquid polymer and a solid polymer. The polymers appear to be polystyrenes. 

Some routes to (SN), that do not involve (SN)2 as an intermediate are available (see 15.2.12.3). The polymer is obtained in high yield from the reaction of (NSC1)3 with trimethylsilyl azide in acetonitrile - , by the electrochemical reduction of [(SN)5] salts ", and by radiofrequency discharge through (SN)4 vapors in a helium plasma. Other reactions that produce (SN), include the reduction of S2N" with azide ion, the solid state polymerization of impure S4N2 (recrystallized S4N2 does not polymerize) , and the oxidation of (SN)J with certain electrophiles . 

Chinn J A, Horbett T A, Ratner B D, Schway M B, Hague Y and Hauschka S D 1989 Enhancement of serum fibroneotin adsorption and the clonal plating of swiss mouse-3T3 fibroplast and MM14-mouse myoblast cells on polymer substrates modified by radiofrequency plasma deposition J. Colloid Interface Sol. 127 67-87... 

A rubber-like (NPCl2) polymer is formed in low yield by exposure of (NPCl2)s to a low-pressure radiofrequency plasma. ... 

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