Polymer polyvinylpyridine

Mobile-phase selection for cationic polymers is similar to that for the other polymers in that ionic strength and pH can change the shape of the solute from linear to globular (9). Mobile phases are often low pH e.g., 0.1% trifluo-roacetic acid, including 0.2 M sodium chloride, has been used successfully for polyvinylpyridines. Sodium nitrate can be substituted for the chloride to avoid corrosive effects. Some salt must be included so that ion exclusion does not occur (3). 

In the theoretical treatment of ion exchange polymers the roles of charge propagation and of migration of ions were further studied by digital simulation. Another example of proven 3-dimensional redox catalysis of the oxidation of Ks[Fe(CN)5] at a ruthenium modified polyvinylpyridine coated electrode was reported... 

The redox active polymer films might bear the mediator group attached either covalently to the polymer backbone (polyvinylferrocene, Ru(II) complexes of polyvinylpyridine, etc.) or electrostatically within the ion-exchange polymer (e.g. in Nation, cf. Section 2.6). 

Protective Colloids. Another approach in preparing and stabilizing metal colloids is by adsorption of macromolecules on their surfaces. A wide variety of materials have been used including gummy gelatinous liquids,(J 0) albumin,(27) Icelandic moss,(28) latex,(22) polyvinylpyrrolidone, (29) antibodies, ( 30 ) carbowax 20M, ( 31 ) polyvinylpyridine, (31 ) and various polymer-water/oil-water mixtures.( 2) These studies clearly indicate that "steric stabilization of metal colloids is also important (along with electronic stabilization).(33)... 

It should be pointed out that the addition of substances, which could improve the biocompatibility of sol-gel processing and the functional characteristics of the silica matrix, is practiced rather widely. Polyethylene glycol) is one of such additives [110— 113]. Enzyme stabilization was favored by formation of polyelectrolyte complexes with polymers. For example, an increase in the lactate oxidase and glycolate oxidase activity and lifetime took place when they were combined with poly(N-vinylimida-zole) and poly(ethyleneimine), respectively, prior to their immobilization [87,114]. To improve the functional efficiency of entrapped horseradish peroxidase, a graft copolymer of polyvinylimidazole and polyvinylpyridine was added [115,116]. As shown in Refs. [117,118], the denaturation of calcium-binding proteins, cod III parvalbumin and oncomodulin, in the course of sol-gel processing could be decreased by complexation with calcium cations. 

Many borohydrides are highly unstable and have to be used as freshly prepared ethereal solutions. However there are instances where the polymer-supported versions are more stable e. g. an Amberlyst anion exchange resin supported borohydride and cyanoborohydride [61], polyvinylpyridine supported zinc borohydride [62] and the corresponding zirconium borohydride [63]. Such compounds, in their labeled forms, should turn out to be very useful. 

Scheme II. Schematic representation of sulfonated metalloporphyrins supported on different polyvinylpyridine polymers and Amberlite-IRA-900.

Thus one might expect flexible, water-soluble synthetic polymers with suitable side chains to show strong affinities for small molecules. In the course of 20 years we examined the binding ability of polyvinylpyrrolidone, polyvinylpyridine, polylysine, polyacrylamide, polyisopro-pylacrylamide, polyvinylimidazole, polyvinylmethyloxazolidinone,... 

Nafion (17) is a perfluorinated polymer related to teflon (polytetrafluoroethylene). An electrode is conveniently coated by allowing an ethanolic solution of the polymer to evaporate. The film produced is stable, rather more so in fact than other polymer films, e.g. polyvinylpyridine (see Section 57.3.2.2). At the microscopic level the polymer separates into two phases, the bulk polymer and the lower density ionic cluster phase. Diffusion of ions can occur quite freely for example, the diffusion coefficient of Na+ in Nafion (MW 1200) is only slightly less than in water.44... 

Once DNA has been condensed by a polycation, it is important for these complexes to retain a certain level of stability in salt solutions to allow sufficient time for cellular uptake of the particles. Izumrudov et al. (1999) studied the stability of a variety of polymers including polyvinylpyridines, linear poly amines, branched polyamines, polymethacrylates, and polyamides in salt solutions at a variety of pHs. They observed that polymers with predominantly primary amines produced the most stable polymer/DNA complexes followed by tertiary then quaternary amines, while higher molecular weight polymers resulted in more stable complexes for all amine types. Thus, it may be possible to specifically control complex stability by adjusting the relative amount of each amine type in the polymer. 

Salen-type complexes have been immobilized by coordinative bonding on polyvinylpyridine-type polymers (97). However, ee values did not exceed 46%. The retention of the complex on the polymer was reported to be excellent. 

Thus one might expect flexible, water-soluble synthetic polymers with suitable side chains to show affinities for small molecules. We have examined, over several decades, the binding ability of poly(vinylpyrrolidone), polyvinylpyridine, polylysine, polyacrylamide, poly(isopropylacrylamide), poly(vinylimidazole), poly(vinylmethyloxazolidi-none), poly(vinylmethyloxazolidinone-vinylimidazole), poly(vinylpyrrolidone-vinyli-midazole), poly(vinylpyrrolidone-vinyl alcohol), poly(vinylpyrrolidone-maleic anhydride), poly(vinylmethyloxazolidinone-maleic anhydride), and poly(2-methylami-noethyl methylacrylate-methacrylic acid). Other investigators have studied similar synthetic polymers [5-12], In our experience no water-soluble polymer binds small molecules with an avidity comparable to serum albumin. 

Cordes and co-workers 191 found that the alkaline hydrolysis of p-nitrophenyl hexanoate is subject to catalysis by polyvinylpyridine-based polysoaps. For example, k bs is increased from 0.1 mm to 1.4 mm in the presence of 5 x 10 7 M 38% polysoap (23) (the same material used in the Strauss work). With 5 x 10-7 M polymer having a 15 % dodecyl content, the rate is increased only 3 times above background. The simplest rationale for the kinetics invokes both hydrophobic and electrostatic forces. Thus, dodecyl chains on the polymer hydrophobically bind p-nitrophenyl hexanoate to the polymer surface. Since the polymer possesses a high density of cationic nitrogens, hydroxide ions also accumulate at the polymer surface where they catalyze the hydrolysis of bound ester. Addition of nitrate ion to the aqueous reaction... 

Adsorption. Adsorption can be reversible or irreversible. This method has been used particularly for the preparation of polymer-modified electrodes. A solution of polymer is either painted on the electrode and the solvent evaporated, or the electrode is immersed in a solution of the polymer. Relevant examples are polymers that let charge pass through the film polyvinylpyridine (PVP), polyvinylferrocene (PVF), porphyrins, and phthalocyanines. Direct deposition in the gas phase or sputtering are also possible. 

Mao L, Yamamoto K (2000) Amperometric biosensor for glutathione based on osmium-polyvinylpyridine gel polymer and glutathione sulfhydryl oxidase. Electroanalysis 12 ... 

In addition to recent advances in block co-polymer templating of periodic mesoporous silica and silica colloidal crystal templating of periodic mesopo-rous polymers [79], SAMs have been used for polymer patterning [80]. Mixtures of two strongly incompatible polymers, a polystyrene (PS)-polyvinylpyridine (PVP) blend, were found to phase separate when placed on a... 

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