Effect of polymer composition on the production of cationic multihollow polymer particles by the stepwise acid/alkali method

The effect of the polymer composition on the formation of multihollow structures formed within submicron-sized styrene–butyl acrylate–dimethylaminoethyl methacrylate terpolymer particles by the “acid/alkali method” proposed by the authors was examined. The cationic particles were produced by seeded emulsion terpolymerization with 2,2′-azobis(2-amidinopropane) hydrochloride initiator. The dimethylaminoethyl methacrylate content and the glass-transition temperature of the terpolymer greatly affected the formation of the multihollow structure. Received: 3 December 1998 Accepted in revised form: 4 February 1999     

Features of formation of magnetite coatings on low-carbon steel in hot nitrate solutions

The process of anticorrosion magnetite coating (MC) formation on low-carbon steel is studied in alkali-free nitrate converting media at the temperatures of 70–98°C reduced as compared to those used (130–145°C) in standard technologies of steel bluing: formation of such coatings in alkaline nitrate solutions. Alongside with the conventional corrosion-electrochemical methods of analysis of the formed MCs, the regularities of the MC surface reliefs were studied using the method of atomic force microscopy combined with the technique of flicker-noise spectroscopy (FNS) for processing digitized images and obtaining the parameters of the MC surface structure in different nanometer ranges. It was shown that it is necessary to introduce additives of metal nitrates with a low cation radius into the ammonium nitrate converting solution to obtain MCs with a high corrosion stability at the first stage of MC formation and the final stage must consist in the further “passivation” of MCs: MC treatment by aqueous solutions based on nontoxic carboxylates. According to the FNS analysis of the surface structure of the formed MCs, a significant decrease of the FNS “point” factor, an indicator of MC corrosion instability, occurred during the final treatment. On this basis, one could characterize quantitatively the results of accelerated corrosion tests: no steel corrosion occurred on the thus formed coatings for 42 days under standard severe conditions: 100% relative humidity and daily “showering”. The performed study reveals fundamental possibilities for solving the problems of standardization of the anticorrosion coating surface based on the analysis of their surface profile in the nanometer range.     

Anion Nature Influence on Spectral and Some Physico-Chemical Properties of 6,7-Dihydroxy-4-methyl-2-phenylchromenylium Salts

The influence of the nature of anions (Cl–, Br–, I–, ClO4–, and PF6–) on the physico-chemical properties (solubility, solvatochromism, and spectral characteristics) of 6,7-dihydroxy-4-methyl-2-phenylchromenylium salts was studied. The main spectrophotometric characteristics were determined. It was noted that the molar absorption coefficient increases on passing to polar solvents. The highest molar absorption coefficient was observed for the hexafluorophosphate anion, which has weak coordinating power that favors more efficient solvation of the organic cation.     

Synthesis and structure of tricyclic quinazoline alkaloid oxalates

Oxalates of the alkaloids deoxyvasicinone, 2,3-tetra-, and their seven-membered analog 2,3-pentamethylen-3,4-dihydroquinazol-4-one and the complex of 2,3-pentamethylen-3,4-dihydroquinazol-4-one hydrochloride with oxalic acid were synthesized. It was found that 2:1, 2:1, and 1:1 alkaloid:oxalic acid complexes, respectively, were formed. The last complex had 2,3-pentamethylen-3,4-dihydroquinazol-4-one, oxalic acid, and HCl in a 2:1:2 ratio, respectively. X-ray crystal structures of single crystals were performed. The oxalate of 2,3-pentamethylen-3,4-dihydroquinazol-4-one and its hydrochloride formed salts with a protonated N1 atom and involvement of only one hydroxyl. The other alkaloids formed a complex with oxalic acid through N1…H-O H-bonds involving both acid hydroxyls. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 152–156, March–April, 2007.     

Anion Effects on Sodium Ion and Acid Molecule Adduction to Protein Ions in Electrospray Ionization Mass Spectrometry

Gaseous protein–metal ion and protein–molecule complexes can be readily formed by electrospray ionization (ESI) from aqueous solutions containing proteins and millimolar concentrations of sodium salts of various anions. The extent of sodium and acid molecule adduction to multiply charged protein ions is inversely related and depends strongly on the proton affinity (PA) of the anion, with extensive sodium adduction occurring for anions with PA values greater than ~300 kcal·mol^–1 and extensive acid molecule adduction occurring for anions with PA values less than 315 kcal·mol^–1. The role of the anion on the extent of sodium and acid molecule adduction does not directly follow the Hofmeister series, suggesting that direct protein–ion interactions may not play a significant role in the observed effect of anions on protein structure in solution. These results indicate that salts with anions that have low PA values may be useful solution-phase additives to minimize nonspecific metal ion adduction in ESI experiments designed to identify specific protein-metal ion interactions.     

Photomagnetic hybrid ultrathin films

Two novel types of photomagnetic hybrid ultrathin film (film A and B) of metal cyanides have been fabricated by means of the modified Langmuir–Blodgett method using a smectite clay mineral. Film A is composed of an amphiphilic azobenzene cation, a montmorillonite, and Prussian Blue in which photocontrol in the magnetization was realized by the photoisomerization of azobenzene chromophore. The observed photomagnetic efficiency was large (ca. 11%) due to the well-organized structure of the ultrathin film. Film B is composed of a quaternary ammonium salt, a montmorillonite, and Co–Fe Prussian Blue in which the photoinduced magnetization caused by the electron transfer exhibited an anisotropic response with regards to the direction of the applied magnetic field. This phenomenon is ascribed to the unique structure of Co–Fe Prussian Blue formed onto the clay layer. Contribution to special issue “Magnetic field effects in Electrochemistry”     

Composition,structure, and ir spectra of acid trialkylmethylammonium acetates in CCl4+HAc solutions

The composition and structure of neutral and acid trialkyl(C₈-C₁₀)methylammonium acetates in CCl₄+HAc solutions formed by the reaction R₃CH₃N⁺Ac⁻+nHAc⇔R₃CH₃N⁺(Ac·nAc)⁻ are investigated by IR spectroscopy. As the molar ratio HAc/R₃CH₃N⁺Ac⁻ increases in solutions, complex anions Ac·nAc⁻ (I) with n=1, 2, 3, 4 are formed in sequence. The curves of formation of anions with n=0, 1, 2 are plotted. One terminal COO group of anions I is bonded to (“blocked” by) the R₃CH₃N⁺ cation, and another group sequentially adds H-bonded HAc molecules as the concentration of HAc in solutions increases. The sequence of IR spectral changes in the series of anions I with n=0, 1, 2, 3, 4 is discussed. Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 2, pp. 310–318, March–April, 1996. Translated by L. Smolina     

Nucleophilic reactivity of the peroxide anion in aqueous-alcoholic solutions in the presence of detergents

The reactivity of hydroxide and peroxide anions with 4-nitrophenyl N,N-dimethylcarbamate in aqueous-alcoholic detergent media and in “oil in water” microemulsions has been studied. Aqueous-alcoholic solutions of cationic (CTAB) and neutral (Triton X-100) surface active substances have promise for decomposition of substrates by a nucleophilic mechanism. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 6, pp. 358–363, November–December, 2007.     

Enthalpies of reaction of calcium chloride and sodium oxalate in an aqueous NaCl solution

The heats of mixing of dilute aqueous solutions of calcium chloride and sodium oxalate with additions of 1–5 wt % NaCl at 298.15 K and the heats of dilution of calcium chloride solutions were measured. Increasing the sodium chloride content in a solution noticeably increases the time of precipitation of calcium oxalate. A fine precipitate of CaC₂O₄ formed in solutions containing 3 and 5 wt % NaCl is difficult to remove from the parts of a calorimeter cell. The enthalpies of precipitation of CaC₂O₄ depend slightly on the content of the “background electrolyte,” whereas the enthalpies of dilution, owing to ion association, significantly decrease in magnitude and become positive in a 5% NaCl solution. The “standard” enthalpy of precipitation in water, determined by extrapolation of the experimental values to the zero concentration of the background electrolyte, differs noticeably from the enthalpy of precipitation in water.     

Crystallization and melting behavior of low molar weight PEO–PPO–PEO triblock copolymers

The crystallization behavior of a series of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymers (Pluronics) was investigated using time-resolved small-angle X-ray scattering (SAXS), thermal analysis, and polarized optical microscopy. For comparison, a PEO homopolymer, PEO3K, was also included. Time-resolved SAXS during the crystallization of PEO3K shows a typical “two-step” process, i.e., in the initial stage, a metastable crystal with nonintegral folding (NIF) structure forms first, then, it transforms into integral folding (IF) structures, the IF(0) and the IF(1). In contrast with PEO3K, the PEO–PPO–PEO triblock copolymers show a “one-step” crystallization process, i.e., the PEO blocks crystallize directly into the final state and do not change with time. In thermal analysis, only one major solid–melt transition is observed during isothermal crystallization and subsequent melting for triblock copolymers. In the full temperature range, a linear crystal growth is observed. The crystal growth rates monotonously decrease with crystallization temperatures. Notches or breaks due to the NIF–IF transition as clearly seen for PEO3K cannot be recognized for Pluronics. Based on these results, we conclude that the crystallization of PEO–PPO–PEO triblock copolymers follows a “one-step” process; no metastable structure serving as an intermediate state is formed during the crystallization process within the time scale of the current experiments (<120 min).     

Evaluation of high-performance liquid chromatography for determination of phenolic compounds in pear horticultural cultivars

Summary An analytical evaluation of an HPLC method with diode array detection to separate and quantify polyphenolic compounds from pears has been made. The method was applied to the quantitative analysis of phenolics from five pear horticultural cultivars (“Agua”, “Blanquilla”, “Conference”, “Pasagrana” and “Decana”) in both peel and pulp matrices and evaluated for precision and accuracy. Precision was taken as the reproducibility in peak area of the polyphenols of interest as well as in the slope of calibration graphs. Values ranged 2–5%. Accuracy was evaluated by recovery of all polyphenolic compounds from both peel and pulp in all pears investigated. Accuracy values ranged 92–102%, and were independent of the polyphenolic structure, horticultural cultivar and matrix. Identification was by comparing retention times and UV spectra with those of standards when commercially available. When not available commercially, provisional identification was according to spectral characteristics as well as from isolation and hydrolysis data. Application of the method revealed differences between peel and pulp in all cases studied; the higher levels of phenolics were found in the peels. “Decana” and “Pasagrana” cultivars showed the highest phenolic content compounds whereas “Conference” showed the lowest.     

Radiotracer technique in the study of molecular complexes. Transference number of alcohol-iodine “inner charge-transfer complexes”

The radiotracer technique has been applied to find the transference number of anion/cation constituents of iodine-alcohols “inner chargetransfer complexes” and it is deduced that the anions are the main charge carriers.     

“Perfect” structure regions in amorphous argon

The structure of molecular dynamic models of amorphous argon is investigated by the Voronoi-Delaunay method. It is shown that the majority of Delaunay simplices (determined by quadruplets of the nearest atoms) are “perfect,” i.e., close in their shape either to the ideal tetrahedron or to the ideal quartoctahedron. These two types of structural elements are positioned in a correlated manner relative to each other, forming regions of a “perfect” structure which, however, is not crystalline. The regions themselves are separated by sections of an “imperfect” structure in which the shape of simplicial atomic configurations differs from the mentioned ideal forms. Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 53–63, January–February, 1994. Translated by L. Chernomorskaya     

Structural transition to electrolyte-water solvent and changes in the molecular dynamics of water and properties of solutions

A model of concentration transition “ions and complexes in a water structure → ionic and ionicaqueous clusters → polymer structures of salt and crystal hydrate melts” is suggested. The appearance of cluster nanostructures outside the first zone of a waterlike structure is regarded as a general characteristic of solutions. The characteristics of solutions, phase equilibria, and salts of complex composition are interpreted based on this model. Investigation of the complex dielectric constant of electrolytic solutions in the SHF and EHF bands (7–119 GHz) at high concentrations showed that there are two dispersion regions in which the relaxation times differ by a factor of 5–10. Relaxation processes are separated, the numbers of molecules in hydration shells are calculated, and relaxation times are determined for bulky tetrahedral water with hydration shells of ions, for clusters, and for ionicaqueous polymer chains. It is shown that the two structure subsystems of water molecules in concentrated solutions may be described using the limited rotator/generalized diffusion molecular model. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 5, pp. 851–863, September–October, 1998.     

Nature of weak inter-and intramolecular interactions in crystals 7. Stability of homochiral supramolecular organization of dications in crystals of 1,3-dialkyl-4,5-bis(3-guanidinioamino)imidazolidin-2-one salts

The geometries and peculiarities of the electronic structure of chiral 1,3-dialkyl-4,5-bis(3-guanidinioamino)imidazolidin-2-one dications (C ₂ symmetry) and their associates in salts containing chloride and nitrate anions were studied by X-ray diffraction analysis and quantum chemistry methods. Homochiral H-bonded cation chains are stable supramolecular fragments; however, their presence in the crystal structures does not provide spontaneous resolution of racemates upon crystallization. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 387–395, March, 2006.     

Nucleophilic reactivity of the peroxide anion in microemulsions of the “oil-in-water” type in the decomposition of phosphate and toluenesulfonate esters

The kinetics of the reaction of the 4-nitrophenyl esters of diethylphosphoric and 4-toluenesulfonic acids with HO^– and HOO^– anions in microemulsions of the “oil-in-water” type was studied. It was shown that the reactivity of the HOO^– anion depends on the nature of the detergent forming the microemulsion and decreases in the order cetyltrimethylammonium bromide > Triton X-100 > sodium dodecyl sulfate. It was established that concentration of the reagents on the surface of the microdrops leads to an increase of 2–3 orders of magnitude in the rate during the transition from aqueous solutions to the microemulsion.     

Packing of complex anions and effect of mutual ordering of heavy cations in structures with the paratungstate ion [H2W12O42]10−

The packing of [H ₂W₁₂O₄₂]¹⁰⁻ polyanions in seven known crystal structures is analyzed. The centers of the polyanions are arranged according to the law of the F- cell (3 cases) or I- cell (2 cases) or according to a more complex law. “Coherence” in the arrangement of heavy W atoms belonging to different polyanions is established: there are crystallographic planes with high concentrations of these atoms;this is an effect of superstructural ordering up to formation of the cation sublattice with light “filler” atoms (K, Mg, Na, N) partly addressed to the sites of the sublattice. Translated fromZhumal Strukturnoi Khimii, Vol. 38, No. 4, pp. 732–738, July–August, 1997.     

peri-Naphthylenediamines

Tertiary alcohols containing the 4,5-bis(dimethylamino)-1-naphthyl group were synthesized. The carbocations that formed from α-methyl-containing alcohols in an acidic medium underwent smooth El elimination to give the corresponding unsaturated derivatives of the “proton sponge” in good yields. At the same time, the carbocation generated from 4-(α-hydroxybenzhydryl)-1,8-bis(dimethylamino)naphthalene was converted into a benzo-[a]fluorene derivative as a result of a complex reaction which has been previously unknown in the chemistry of “proton sponges.” The structure of the latter derivative was established by X-ray diffraction analysis. For Part 26, see Ref. 1; this paper simultaneously presents Part 5 of the series “Resonance-stabilized α-naphthylmethyl carbocations and derived spiro compounds;” for Part 4, see Ref. 2. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1103–1108, June, 2000.     

Dimerization and protonation reactions of nitrosonitrobenzenes radical anions

The electrochemical behavior of 2-, 3-, and 4-nitrosonitrobenzenes (NNB) in DMF (with Bu₄NClO₄ suppoting salt) in the presence and in the absence of different proton donors (water, phenol, benzoic, acetic, chloroacetic, and sulfuric acids) is studied by the methods of cyclic voltammetry, chronoamperometry and also by electrolysis at the controlled potential. The electrochemical reduction of these compounds is shown to preferentially afford either monomeric (N-nitrophenylhydroxylamines) or dimeric (azoxy compounds) products, which is determined by the interplay between reactions of protonation and dimerization of NNB radical anions. The dimerization reactions proceed fast and reversibly to afford the corresponding dimeric dianions with the basicity much higher as compared with NNB radical anions as the result of which the monomeric products are formed in the presence of “strong” proton donors and the dimeric products form in the presence of “weak” proton donors. Like the effective rate of formation of dimeric products, the basicity of radical anions increases in the row 4- < 3- < 2-NNB.     

First radical cation salts of 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP) with copper(II) metal complex anions: β-(BDA-TTP)4Cu2Cl6 and (BDA-TTP)2CuCl4

New radical cation salts based on 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP) with copper(II) metal complex anions, β-(BDA-TTP)₄Cu₂Cl₆ and (BDA-TTP)₂CuCl₄, were synthesized and structurally characterized. Single crystals were prepared by electrochemical oxidation of BDA-TTP under galvanostatic conditions. X-ray diffraction study demonstrated that the salts have a layered structure, in which the conducting BDA-TTP layers alternate with the [Cu₂Cl₆]²⁻ or [CuCl₄]²⁻ anions. Both salts show the semiconductor-type temperature dependence of the conductivity. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 48–54, January, 2007.