Metallic in polymer

In the many reports on photoelectron spectroscopy, studies on the interface formation between PPVs and metals, focus mainly on the two most commonly used top electrode metals in polymer light emitting device structures, namely aluminum [55-62] and calcium [62-67]. Other metals studied include chromium [55, 68], gold [69], nickel [69], sodium [70, 71], and rubidium [72], For the cases of nickel, gold, and chromium deposited on top of the polymer surfaces, interactions with the polymers are reported [55, 68]. In the case of the interface between PPV on top of metallic chromium, however, no interaction with the polymer was detected [55]. The results concerning the interaction between chromium and PPV indicates two different effects, namely the polymer-on-metal versus the metal-on-polymer interface formation. Next, the PPV interface formation with aluminum and calcium will be discussed in more detail. 

Hirai, H., Nakao Y., and Toshima, N., Preparation of colloidal transition-metals in polymers by reduction with alcohols or ethers, J. Macromol. Sci. Chem. A, 13, 727, 1979. 

Moore, J. S. Transition Metals in Polymer Synthesis Ring-opening Metathesis Polymerization and Other Transition Metal Polymerization Techniques. In Comprehensive Organometaltic Chemistry // Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds. Elsevier Oxford, 1995 Vol. 12, pp 1209-1232. 

Furthermore, in this type of plasma the polymeric materials deposit not only on the substrate but also on the electrode surfaces. Thus, the sputter deposition of metal in polymer-forming plasmas is more complicated than that in non-polymer-forming plasmas. 

Shear yielding in polymers has much in common with ductility in metals. In polymers, the yielding may be localised into shear bands, which are regions of high shear strain less than 1 m in thickness or the yield zones may be much more diffuse " Under a general state of stress, defined by the three principal stresses Gi, 02 and 03, the condition for yielding is given by a modified von Mises crite-rion l ... 

A different approach was taken by Kumar and associates [61]. Fie also embedded metals in polymers, but used as his precursor the polymer and not the monomer. In his first study a composite material containing amorphous Cu nanoparticles and nanocrystalline CU2O embedded in polyanUine matrices was prepared by a sonochemical method. These composite materials were obtained from the soni-cation of copper (II) acetate when aniline or 1% v/v aniline-water was used as the solvent. Mechanisms for the formation of these products are proposed and discussed. The physical and thermal properties of the as-prepared composite materials are presented. A band gap of 2.61 eV is estimated from optical measurements for the as-prepared CU2O in polyaniline. 

Low nuclear metal clusters (n = 4 to n = 20) of diverse metals in polymers, copolymers and inorganic supports have recently been reported by Ozin286 and have been used as catalysts in the petrochemical industry. Much progress remains to be made in the correlation of catalytic behavior of Pt with the observed electronic properties. The nature of the... 

Unlike diffusion of noble metals in polymers, the extremely low mobility of reactive metals such as Cr and Ti. as reflected in their thermal stability in the aforementioned spectroscopic studies, is obviously not controlled by the availability of free volume. Here diffusion is expected to be frozen in as a result of strong binding to the polymer. 

Beyond an insight into the ease with which compounds can be oxidized or reduced by measuring the formal potential, cyclic voltammetry can be used to determine the rate of electron transfer across the electrode/solution or electrode/film interface. Optimizing the rate of heterogeneous electron transfer is important for technological applications ranging from the analysis of metals in polymers, foods, and cosmetics to the development of biosensors and molecular electronic devices. 

Coates, G.W. and Waymouth, R.M. (1995) Transition metals in polymer synthesis Ziegler-Natta reaction, in Abel, E.W., Stone, F.G.A., Wilkinson, G., Hegedus, L. (eds.). Comprehensive Organometallic Chemistry II, vol. 12, Pergamon Press, New York, pp. 1193-1208. 

These materials are well-known from their active and selective function in biological matter. The increasing knowledge about natural metal-containing macromolecules stimulates chemists to synthesize artificial systems. The newly developed materials can exhibit imusual properties for new apphcations due to the introduction of metals in polymers. Therefore chemists, physicists, biologists, physicians, and engineers are involved in this interdisciplinaric subject where a macromolecule and a metal atom are combined in one material. 

This technique has been applied to determining the identity of oxygen absorbers in polymers [108] also to determine traces of metals in polymers. 

Sources of traces of metals in polymers are neutralising chemicals added to the final stages of manufacture to eliminate the effects of acidic catalyst remnants on polymer processing properties (e.g., hygroscopicity due to residual chloride ion). A case in point is high-density polyethylene (HOPE) and PP produced by the aluminium alkyl-titanium halide route which is treated with sodium hydroxide in the final stages of manufacture. 

AAS is a useful technique for the determination of traces of metals in polymers. Generally, the polymer is ashed at a maximum temperature of 450 °C 0.1 hour from start heat to 200 °C 1-3 hours from start hold at 200 °C 3-5 hours from start heat to 450 °C 5-8 hours from start hold at 450 °C. The ash is digested with warm nitric acid prior to spectrometric analysis. The detection limits for metals in polymers achieved by this procedure are given in Table 11.6. 

Flame and GFAAS techniques have adequate sensitivity for the determination of metals in polymer samples. In this technique up to 1 g of dry sample is digested in a microwave oven for a few minutes with 5 ml of aqua regia in a small polytetrafluoroethylene-lined bomb, and then the bomb washings are transferred to a 50 ml volumetric flask prior to analysis by flame AAS. Detection limits (mg/kg) achieved by this technique were 0.25 (cadmium, zinc) 0.5 (chromium, manganese) 1 (copper, nickel, iron) and 2.5 (lead). Application of this technique gave recoveries ranging between 85% (cadmium) and 101% (lead, nickel, iron) with an overall recovery of 95%. 

An AA spectrometer is also available with a graphite furnace and vapor generation accessories for the trace analysis of lead, antimony, arsenic, and mercury at parts-per-billion levels. AA is used for quantitative analysis of these metals in polymers as well as finished formulations. It has been used to determine the elemental composition of catalysts and plastic additives, polymer formulations, and composite materials. Samples may be rapidly acid digested prior to analysis using a microwave oven or similar techniques. Microwave furnaces are also available for dry ashing. 

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