V. A. Burmistrov

Orientational effects of hydrogen bonding in liquid-crystalline solutions containing Schiff bases

Abstract Intermolecular hydrogen bonding in binary mixtures containing nematogenic Schiff bases as solvents and proton-donating non-mesomorphic solutes has been considered. Reasons for the anomalous concentration dependences of solute order parameters are discussed. A solution structure model of acetic acid in nematic solvents is proposed; constants of complex-dimer equilibrium and coefficients of the orientational correlation of the non-mesogenic solute are calculated on the basis of this model. Hydrogen bonded complex structure using 13C NMR has been studied and stability constants in isotropic solutions in chloroform have been calculated. The influence of the solvent orientational ordering on the complex stability is discussed. Data on the solvation isotopic effects in the solutions investigated, which confirm the adequacy of the model are given.

2D M-nanoaggregates in langmuir layers of calamite mesogen

It is shown that a representative of calamite mesogens, 4-(4′-nonyloxyphenylazo)cinnamic acid (NOPCA), forms floating monolayers on the surface of water at initial surface coverage c ≤ 22.8%; their structural elements are 2D face-on M-nanoaggregates. The main structure characteristics and properties of M-monolayers (the size of M-nanoaggregates formed in the layer, number of molecules in them, distance between the aggregates, water content in the aggregates and between them, compressibility, and pressure and surface concentration ranges of existence of the aggregates) are determined. It is shown that this compound manifests a specific behavior in Langmuir layers that is different from most of the compounds studied so far due to particularities of the molecular structure and formation of hydrogen bonds in layers on the surface of water. The formation of two types of floating NOPCA monolayers is observed and changes of their characteristics are studied in successive “compression-decompression” cycles.

Specific features of the formation of zinc and cadmium complexes with tetraphenylporphine in amphiprotic media

The kinetics of the complex formation reactions of tetraphenylporphine with zinc and cadmium acetates in mixed solvents containing alcohols and inert diluents was studied by electronic absorption spectroscopy. The dependences of the rate constant on the binary solvent composition have an extreme character, which is universal in the temperature range 298–313 K for different salts, alcohols, and weakly solvating diluents. The electric conductivity of zinc acetate solutions was measured in a wide range of compositions of alcohol-chloroform binary solvents. The electric conductivity increased with an increase in the content of alcohols.

Volatility of some aromatic nitrosubstituted plasticizers for polymers

Nine derivatives of nitrophthalic acids and nitrophenols were synthesized as potential plasticizers for polymers and structurally characterized by 1H NMR and elemental analysis. The time dependences of the weight loss for the nitro derivatives synthesized and for commercial plasticizers (dibutyl phthalate and dioctyl phthalate) were obtained by gravimetric method at 100ºC, and their volatilities and dipole moments were calculated. The resultant nitroplasticizers are considerably less volatile than dibutyl phthalate. Low volatility is associated not so much with high molecular weight as with high polarity. The nitroplasticizers are well compatible with cellulose esters and exhibit low rates of migration from polymer films.

Influence of a cellulose diacetate matrix on the complexation kinetics of tetraphenylporphin with Zn and Cd

The dependence of the reaction rate of tetraphenylporphin zinc and cadmium complexes in a polymer matrix on a base of cellulose diacetate and low-molecular model solutions was investigated. The characteristics of the diffusive transport of aqueous solutions of zinc and cadmium acetates through the cellulose diacetate membrane were obtained. The kinetic control of the porphyrin reaction incorporated into the polymer, and the determining influence of the steric limitations of the matrix of a rigid chain polymer on macroheterocycle deformation (and thus its reactivity) are shown.

Modern Advances in the Preparation and Modification of Cellulose Nitrates

The published data on the preparation of cellulose nitrate are summarized. New sources of cellulosic materials are analyzed. The results of studies on the chemical modification of cellulose nitrate by nucleophilic substitution are presented. The published data on the plasticization of cellulose nitrate are summarized. Modern plasticizing systems and methods for their effectiveness assessment are described.

Dielectric and orientation effects of ‘classical’ and supramolecular liquid crystals self-assembly

ABSTRACT Fragments of phase diagrams of binary systems containing 4-pentyloxy-4ʹ-cyanobiphenyl (5OCB) and 4-(ω-hydroxyalkyloxy)-4ʹ-cyanobiphenyl (HO3OCB, HO6OCB and HO9OCB) were obtained. The temperature range expansion of the nematic phase at mixing of the components was established. The dielectric and optical properties of binary mixtures were studied. A significant increase in the dielectric anisotropy was observed when the ‘classical’ liquid crystal (LC) was mixed with supramolecular HOnOCB. From the data on birefringence and the 1H NMR spectra, temperature dependences of the orientational order parameter of the ‘classical’ LC + supramolecular LC systems were obtained. There is a good agreement between S values obtained by independent methods. The invariability of the order parameter at mixing 5OCB with HO3OCB and HO9OCB and some growth in systems containing HO6OCB were observed. On the basis of quantum chemical calculations, the analysis of the most probable types of components association in the systems 5ОСВ + HOnOCB was carried out. From the analysis of Kirkwood correlation factors, the main role of competition between the two mechanisms of intermolecular interaction was revealed. ABSTRACT

The mechanisms of porphyrin complexation in solvents and polymer matrices

Experimental data for the reactions of porphyrins with metal salts in various media are analyzed; possible mechanisms of the reactions are discussed. The experimental findings as well as quantum chemical calculations suggest that the most probable reaction mechanism should involve the formation of a SAT complex and a substantial deformation of the macrocycle.