Polyvinylpyrrolidone systemic reactions

Bell et al. (2002) investigated the relationship between water mobility as measured by oxygen-17 NMR (transverse relaxation rate obtained from linewidth at half-height) and chemical stability in glassy and rubbery polyvinylpyrrolidone (PVP) systems. Reported results suggest that water mobility in PVP model systems was not related to Tg. The study did not find a link between water mobility and reaction kinetics data (half-lives) for degradation of aspartame, loss of thiamin and glycine, and stability of invertase. 

A large number of macromolecules complementary to PMAA, namely polyvinylpyrrolidone, polyvinylpyridine, polyacrylamide, poly(vinyl alcohol), poly(ethylene oxide), oligoethylenimine, poly(sodium styrene sulfonate), polycations of the integral type ionen (2X) were used as P2 and P3. The pH of the media strongly influences the studied reactions of complex formation. For example, in PVPy + PVP + PMAA or OEI + PEO + PMAA systems in the add region, where weak polybases are completely protonized and PMAA does practically not dissodate, complexes with hydrogen bonds (PMAA-PVP or PMAA-PEO) are formed. In neutral medium weak polybases are partially ionizated and polyelectrolyte complexes (PMAA-PVPy, PMAA-OEI) are generated. In the alkaline medium formation of complexes has not been observed. 

The features of initiation of free radical reactions in polymers by dimers of nitrogen dioxide are considered. The conversion of planar dimers into nitrosyl nitrate in the presence of amide groups of macromolecules has been revealed. Nitrosyl nitrate initiates radical reactions in oxidative primary process of electron transfer with formation of intermediate radical cations and nitric oxide. As a result of subsequent reactions, nitrogen-containing radicals are produced. The dimer conversion has been exhibited by estimation of the oxyaminoxyl radical yield in characteristic reaction of p-benzoquinone with nitrogen dioxide on addition of aromatic polyamide and polyvinylpyrrolidone to reacting system. The isomerisation of planar dimers is efficient in their complexes with amide groups, as confirmed by ab initio calculations. 

As early as 1997, Antonietti and coworkers [167] showed that palladium nanoparticles supported by polystyrene-polyvinylpyrrolidone block copolymer effect the Mizoroki-Heck reaction while retaining a monodisperse size distribution throughout. Very recently, a similar effect was demonstrated for A-vinylimidazole-A-vinylcaprolactam copolymer, in the presence of which a monodisperse palladium sol was generated directly in the reacting system [168]. 

The polymer-supported bimetallic catalyst system PVP-PdCl2-NiCl2/TPPTS/ PPh3 (PVP = polyvinylpyrrolidone) was found to have good activity in the hydro-xycarbonylation of styrene under aqueous-organic two-phase condition and can be reused four times with little loss of catalytic activity. The effects of temperature, CO pressure, and reaction time were studied to obtain optimum reaction conditions (Equation 7.14) [139]. 

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