Conductive polymers solubility

Practical appHcations have been reported for PVP/ceUulosics (108,119,120) and PVP/polysulfones (121,122) in membrane separation technology, eg, in the manufacture of dialysis membranes. Electrically conductive polymers of polyaruline are rendered more soluble and hence easier to process by complexation with PVP (123). Addition of small amounts of PVP to nylon 66 and 610 causes significant morphological changes, resulting in fewer but more regular spherulites (124). 

Because of the aqueous solubiUty of polyelectrolyte precursor polymers, another method of polymer blend formation is possible. The precursor polymer is co-dissolved with a water-soluble matrix polymer, and films of the blend are cast. With heating, the fully conjugated conducting polymer is generated to form the composite film. This technique has been used for poly(arylene vinylenes) with a variety of water-soluble matrix polymers, including polyacrjiamide, poly(ethylene oxide), polyvinylpyrroHdinone, methylceUulose, and hydroxypropylceUulose (139—141). These blends generally exhibit phase-separated morphologies. 

In the field of soluble conducting polymers new data have been published on poly(3-alkylthiophenes " l They show that the solubility of undoped polymers increases with increasing chain length of the substituent in the order n-butyl > ethyl methyl. But, on the other hand, it has turned out that in the doped state the electro-chemically synthesized polymers cannot be dissolved in reasonable concentrations In a very recent paper Feldhues et al. have reported that some poly(3-alkoxythio-phenes) electropolymerized under special experimental conditions are completely soluble in dipolar aprotic solvents in both the undoped and doped states. The molecular weights were determined in the undoped state by a combination of gel-permeation chromatography (GPC), mass spectroscopy and UV/VIS spectroscopy. It was established that the usual chain length of soluble poly(3-methoxthythiophene) consists of six monomer units. 

A large number of conducting polymers can be synthesised via the use of catalysts [28-30], but generally little control can be exercised over the morphology of the product and purification of the material obtained can be problematical. In recent years however, a number of alternative synthetic routes have been devised which involve soluble precursor polymers which can be more easily purified and cast onto substrates, with subsequent conversion (usually by heating) to the desired product, and... 

G Gustafsson, Y Cao, GM Treacy, F Klavetter, N Colaneri, and AJ Heeger, Flexible light-emitting diodes made from soluble conducting polymers, Nature, 357 477-479, 1992. 

S.H. Askari, S.D. Rughooputh, and F. Wudl, Soluble substituted-polyphenylene vinylene (PPV) conducting polymers spectroscopic studies, Synth. Met., 29 E129-E134, 1989. 

Initially alkynes were polymerised by trial and error with the use of Ziegler type recipes and the mechanism for these reactions may well be an insertion type mechanism. Undefined metathesis catalysts of ETM complexes were known to give poly-acetylene in their reaction with alkynes (acetylene) [45] and metallacycles were proposed as intermediates. Since the introduction of well-defined catalysts far better results have been obtained. The mechanism for this reaction is shown in Figure 16.24 [46], The conductive polymers obtained are soluble materials that can be treated and deposited as solutions on a surface. 

Oxireductases in the Enzymatic Synthesis of Water-Soluble Conducting Polymers... 

The use of enzymes as biocatalysts for the synthesis of water-soluble conducting polymers is simple, environmentally benign, and gives yields of over 90% due to the high efficiency of the enzyme catalyst. Since the use of an enzyme solution does not allow the recovery and reuse of the expensive enzyme, well-established strategies of enzyme immobilization onto solid supports have been applied to HRP [22-30]. A recent work reported an alternative method that allows the recycle and reuse of HRP in the biocatalytic synthesis of ICPs. The method is based on the use of a biphasic catalytic system in which the enzyme is encapsulated by simple solubilization into an IL. The main strategy consisted of encapsulating the HRP in room-temperature IPs insoluble in water, and the other components of the reaction... 

Electrically conducting polymer particles such as polypyrrole and polyaniline could also be prepared by dispersion polymerization in aqueous ethanol (31). The oxidation polymerization of pyrrole and aniline has been carried out at the electrode surfaces so far and formed a thin film of conducting polymer. On the other hand, polypyrrole precipitates as particles when an oxidizing reagent is added to a pyrrole dissolved ethanol solution, which contains a water-soluble stabilizer. In this way electrically conducting polymer particles are obtained and, in order to add more function to them, incorporation of functional groups, such as aldehyde to the surface, and silicone treatment were invented (32). 

Anodic oxidation of pyrrole and N-substituted pyrroles results in the formation of polypyrroles in an oxidized state, which can be useful for the preparation of conducting organic polymers.185-188 Oxidation of 2,5-di-substituted pyrroles produces soluble products and no layer of polymers.187 One of the proposed applications of such a layer of conducting polymer is the protection of semiconductor electrodes from photocorrosion.189-191... 

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