M?ssbauer study of dissimilatory reduction of iron contained in glauconite by alkaliphilic bacteria

⁵⁷Fe M?ssbauer investigations of glauconite and new solid phases formed during the process of the bacterial growth in alkaline environment were carried out at room temperature, 78 K and 4.8 K. The magnetically ordered phase formed during bioleaching of glauconite by G. ferrihydriticus in pure culture or in combination with Cl. alkalicellulosi represented as a mixture of off-stoichiometric magnetite and maghemite. In case of combined binary bacterium culture growth the relative content of magnetically ordered phase was more than for the G. ferrihydriticus growth.     

A convenient one‐pot synthesis of 1,2‐azaphospholanium salts

A novel facile one‐pot synthesis of the 1,2‐azaphospholanes by intramolecular alkylation of 3‐halopropyl amides of tricoordinate phosphorus has been suggested. Using this method, a series of the differently N‐substituted 1,2‐azaphospholanium salts were synthesized. 3‐Aminopropylphosphine oxides were obtained by hydrolysis of the salts. A probable mechanism of the 1,2‐azaphospholanium salts formation is discussed. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:596–602, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10209     

C‐phosphorylated pyrrolylcarbaldehydes

Application of N,N‐dimethylhydrazone protective group for synthesis of C‐phosphorylated aldehydes of the pyrrole series was studied. Removal of the hydrazone protection in monophosphorylated pyrrolylcarbaldehyde hydrazones occurs smoothly, while in biphosphorylated derivatives it results in nitrile formation. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:258–261, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10137     

Copolymerization of N,N‐Dimethylacrylamide with Styrene and Butadiene: The First Example of Polar Growing Chain End/Nonpolar Monomer Cross‐Initiation

Living potassium poly(N,N‐dimethylacrylamide) initiates the polymerization of styrene and butadiene, and adds 1,1‐diphenylethylene in THF solution. The model compound α‐potassio‐N,N‐dimethylpropionamide also polymerizes styrene and butadiene in contrast to esterenolates, which are known to be incapable of such reactions. The IR spectra and SEC traces of the polymers obtained unequivocally prove that styrene and butadiene initiation proceeds directly via the amidoenolate anion. Apparently, this is the first case observed where the polymerization of a nonpolar monomer can be initiated by the growing chain end of a polar polymer.     

Influence of crosslinking conditions on the phase behavior of a polyacrylate-based liquid-crystalline elastomer

The influence of crosslinking conditions (γ-radiation-induced and chemical crosslinking above and below the clearing point) on the phase behavior of a liquid-crystalline polyacrylate-based elastomer is shown and discussed. The network formation in samples γ-irradiated in the nematic phase results in an increase of the clearing point T_n-i which does not depend on the crosslinking density expressed as the ratio of weight-average molecular weight over number-average molecular weight between crosslinks M _w/M _c within a wide M _w/M _c range. The distorting action of the crosslinking agent at the same temperature leads to the opposite tendency in the change of T_n-i. Crosslinking in the isotropic phase shows a strong decrease in T_n-i.     

Conformational changes in poly(vinyl alcohol)-graft-polyacrylamide in aqueous solutions vs graft content

Conformational changes have been studied in intramolecular polymer-polymer complexes (intraPC) of graft copolymers of poly(acrylamide) and poly(vinyl alcohol) (PVA-g-PAA) with various numbers of grafts (4-42) per molecule as a function of temperature and copolymer concentration. It is shown that the magnitude of conformational change depends on the grafts content while the temperature range over which the conformation changes occur is essentially determined by copolymer concentration. The conformational changes are reversible on heating and cooling.     

Polymer-colloid complexes in three-component system: poly(styrene-alt-maleic acid)-poly(ethylene oxide)-silica sol in aqueous medium

Complex formation in the model three-component system, including polymer-polymer complex of poly(styrene-alt-maleic acid) (PSMA) and poly(ethylene oxide) (PEO), and also silica sol (SiO₂) in aqueous solution as a function of molecular weight of PEO and the order of component mixing, were investigated. The degree of binding of PSMA links with PEO and SiO₂ as well as the Gibbs energy of formation of the polymer-polymer complex and polymer-colloid complexes were defined. It was shown that the main factor of stabilization of the structure is hydrogen bonds. The conditions of three-component polymer-colloid system are practically independent of the order of component mixing. The spontaneous formation of polymer-colloid complexes between chemically complementary polymers and small dispersed particles is considered as the main reason for the abnormally high binding ability of colloid particles to the polymer-polymer complex.     

About the compatibility of polymer components in polymer complexes based on poly(acrylamide) and poly(vinyl alcohol)

The issue of applying the usual concepts of polymer compatibility to nonstoichiometric PVA/PAA mixtures of chemically complementary poly(vinyl alcohol) and poly(acrylamide), which form in water solution InterPC (intermolecular polymer complex) stabilyzed by H‐bonds, and PAA to PVA graft copolymers (PVA‐PAA_N) with different grafted chains number N, that are IntraPC (intramolecular polymer complexes) is discussed. PVA and PAA are compatible on molecular level. At the same time PVA/PAA mixture (50/50 W/W) is characterized by heterogeneous structure consists of InterPC with ϕ_char=9g_PVA/g_PAA and the excess of unconnected PAA. In the case of IntraPC, yet, only PVA‐PAA_N, where N=25, is characterized by a single glass transition temperature (Tg). At larger values of N separate PAA domains form giving rise to the corresponding Tg. These results are discussed in view of IntraPC structure peculiarities as a function of N investigated by IR spectroscopy.