Of the PVP complexes

The reactivity ratios of the PVP complex and the pyridine complex (fcpvp/kpy) are summarized in Table 7. 

Table 7. When the neutral salt sodium perchlorate is added, the electrostatic domain of the PVP complex is shielded and the reactivity ratio falls to unity.

Figure 2. Catalytic activities of (a) the PVP complexes and (b) the PVP-Cu secondary metal mixed complexes (O) PVP catalyst (9) pyridine catalyst, in methanol, 30°C...

The oxidation rates of XOH were measured for the PVP complexes of the transition metal ions of the 4th series, i.e., Cr, Mn, Fe, Co, Ni, Cu and Zn ion. As can be seen in Fig. 2 (a), the Cu complexes exhibit the highest activity and the activity of the PVP-Cu catalyst is higher than that of the monomeric pyridine-Cu catalyst. To this Cu complex, equivalent amount of the second metal component was added i.e., the PVP-Cu, secondary metal ion mixed complexes were prepared. The activities of these mixed complexes are summarized in Fig. 2 (b). One notices that Mn ion increases the catalytic activity of the Cu ion although Cr and Fe ion inhibit the catalytic activity. Another important result in Fig. 2 (b) is that the effect of secondary metal ion is more clearly observed in the PVP system, comparing to the monomeric pyridine catalysts. 

In accordance with this data the methods of preparation of C60/PVP complexes containing up to 3% of fullerene (Krakovjak et al., 2005b) and water-soluble C60-fullerene complexes with A -vinylcaprolactam homopolymers and copolymers with 0.75-3.3% of C60-fullerene (Krakovjak et al., 2005a) were worked out. 

Thus, if mentioned above is to be taken into consideration that absorption band in the region of 330-340 nm reflects to a certain extent the degree of fullerene molecules association in solution, we can come to the conclusion that the less the PVP molecular mass and the less the fullerene contents is the more fullerene molecules are in low associated state. It is quite probable that the increase of the fullerene contents in the complex brings to the formation of adducts, where not single fullerene C60 molecules are bonded with PVP but their associates. It can be one of the reasons of the observed fact of the difference of UV-VIS spectra of C60/PVP complex with PVP of different molecular mass (up to spectra crossover, which is a singular evidence that these compounds are nonidentical). 

The abovementioned data show that the spectral characteristics of C60/PVP complexes vary depending on the PVP molecular mass and fullerene content in the complex. Therefore, the quantitative determination of fullerene concentration in such complexes by measuring their absorbance at 336 nm without extraction (Lyon et al., 2006) can give non-reliable results. For quantitative analysis of fullerene in such complexes we used the heterophase and homophase methods, based on destruction and isolation of pure fullerene C60 (Krakovjak et al., 2006). The choice of the method was determined by fullerene concentration - at concentration less... 

However, at the introduction of C60/PVP complex (up to 5 pg/ml) into the cultivating media during cell growth no effects were observed. In the cell MA-104 (cell line derived of green monkey kidney epithelium) grown normally within 3-6 days, no morphological changes and cell metabolism intensiveness were observed (Table 7.1). 

Popov VA, Tyunin MA, Zaitseva OB et al. (2007) Influence of C60/PVP complex on the healing of wounds and the toxicity in the experiments in vivo. In Book of abstracts 8th Biennial International Workshop Fullerenes and Atomic Clusters, July 2-6, St. Peterburg, Russia P173. 

The complexation power of the three polybases towards PAA was easily estimated from potentiometric results PVP > PVME > PEO. The mean stoichiometry of the polymer complex depends on the degree of neutralization of the polyacid, a. 

The suggested rod like structure of the pendant-type FVP-Co(III) complex is supported by the viscosity behavior of the polymer-complex solution (Fig. 3)2 The PVP-Co(III) complexes have higher viscosity than PVP this suggests that the polymer complex has a linear structure and that intra-polymer chelation does not occur. The dependence of the reduced viscosity on dilution and the effect of ionic strength further show that Co(en)2(PVP)Cl] Cl2 is a poly(electrolyte). The polymer complexes with higher x values have a rodlike structure due to electrostatic repulsion or the steric bulkiness of the Co(III) chelate. On the other hand, the solubility and solution behavior of the polymer complex with a lower x value is similar to that of the polymer ligand itself. 

Differential thermal analysis of the PVP-Co(III) complexes also supplied information about the strength of the coordinate bond between Co and FVP5. The dissociation temperature of the coordinate bond increases with degree of coordination (x) 198° (x = 0.17) < 204° (monomeric pyridine complex) < 224°... 

The formation of polymer chelates is independent of the degree of polymerization of the polymer ligand for PVA ligands (DP 400-1400)61 and for PVP ligands (DP 19—108)55. Kavanov etal42 reported that the sedimentation coefficient of the PVP-Cu solution increased from 1 S to 6 S and suggested that polymer ligands associated by Cu complex formation. 

First a complex is prepared between a polymer ligand, eg. PVP,and a metal ion(M,) and a crosslinking agent is added to the solution of the polymer complex. The metal ion M( is (hen removed by treating the resin with an acid. If the conformation of the polymer-ligand chains in this resin remains the best for the metal ion Mj, used as the template, then the resin should preferentially form complexes with the metal ion M j when dipped into a solution containing various metal ions. 

Figure 18 shows the relationship between the degree of coordination (x in 17), ie. the number of positive charges on a polymer chain, and the reactivity ratio (fcpyp/fcpy) for the reaction with Fe(II)-edta2 79). The reactivity ratio increases with x value. Hence, the PVP complex with a higher degree of coordination is considered to have a stronger electrostatic domain because it has more positive charges on the PVP chain. The reactivity ratios ( Qpvp/fcpy) for the partially quaternized PVP(QPVP)-Co(III) complexes 19 are also plotted in Fig. 18. The reactivity ratio...

The activation parameters are presented in Table 819 For the reactions be between the Co(III) complex2+ and Fe-edta2-, (a) to (c) in Table 8, the activation enthalpy is smaller and the activation entropy larger than for the reduction by Fe2+, (d) to (f), which is a reaction of two cations. A comparison of the parameters for the polymer complex, (b) or (c), with those for the pyridine complex, (a) shows that the acceleration for the PVP or QPVP complex is based on a decrease in activation enthalpy and an increase in activation entropy. This is the opposite of the polyelectrolyte-catalyzed reaction, in which the acceleration is due to an increase in activation entropy (compare(e) with (d)). In the polyelectrolyte-catalyzed system the acceleration and increase in activation entropy are attributed to the increase in the local concentration of the two reactants, the Co(HI)-Py complex2 and Fe2+ 84, whereas in the reaction of the polymer complex the large activation entropy and small activation enthalpy are held to be due to the increase in the local concentration of the reactant Fe(II)-edta2 and the electrostatic attraction between the reactant and the Co(III) complex, which is fixed to the polycation chain. 

PVP(DP 98)-Co(Ilf) > PVP(DP 19)-Co(III) > N-ethylimidazole-Co(III) - pyridine-Co(III), and this order agrees with that of the reactivity. The hydrophobic interaction between polymer ligands and Fe(II)(phen)3 is considered to account for the higher reactivity of the polymer complexes. 

The higher reactivity of the PVMI-Co(III) complex is attributed to the electrostatic domain of the polymer complex, as in the above PVP system. When the PVMI chain contracts, the charge density in the polymer domain increases and the reaction rate also increases. On the other hand, when the polymer chain expands, the electrostatic domain is weakened, which produces a fall in reactivity. These results confirm that the conformation of the polymer complex is closely related to the strength of its electrostatic domain and to the reaction rate. The effects of the polymer chain on reactivity are to be understood not only in terms of static chemical environment but also as dynamic effects which vary with the solution conditions, e.g. pH, ionic strength, solvent composition, temperature, and so on. 

A process commonly used to apply PVP to an electrode surface is to allow a solution of the polymer in a solvent such as methanol to evaporate on the surface. The redox active species can be applied by exposing the modified electrode to a solution of the appropriate complex. Alternatively the PVP-redox complex may be formed prior to coating the electrode. A more sophisticated variation of the above technique is spin casting. A small quantity of polymer solution is dropped on to an electrode, e.g. platinum, which is then rotated at thousands of rotations per minute. 

The poly(methacrylic acid)-polyvinylpyrrolidone system have been studied in detail in the series of the homopolymer complexes investigated by the authors (Table 2). The possibility of complex formation in this system has been shown by potentiometry, conductometry and viscometry and also by IR spectroscopic and thermogravimetric investigations of PMAA-PVP complexes in the solid state27,57). 

The association of PMAA-PVP complexe particles in water has been estimated from the weight average molecular weight43) and found by laser light scattering to be... 

As is seen from Table 4, the complexes containing an alternating copolymer as one of the interacting components are rich in the nonionic component (PVP or PEG). Probably part of the PVP(PEG) groups does not participate in the complex formation, due both to the increase of the distance between the active groups in the copolymer and the steric difficulties caused by the bulky anhydride groups. 

A further dependence of the intrinsic viscosity on the content of water-dimethyl sulfoxide mixed solvent for the PVP-MAA/St copolymer system76 has been found the viscosity increases already beyond 30 vol-% of DMSO in the mixture. This indicates the dissociation of the polymer complex. At the same time, in the PMAA-PVP system27, the compact structure of the complex remains intact up to 70 vol-% content of DMSO, i.e. these complexes are very stable to the organic solvent. 

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