N. V. Usol’tseva

Liquid-crystalline polypropyleneimine dendrimer as a stationary phase for gas chromatography

The adsorption properties of a stationary phase for gas chromatography based on a Chromaton N-AW diatomite support modified with a 2K2S16 mesomorphic polypropyleneimine dendrimer are studied. Using the Rohrschneider constants, the studied stationary phase is classified as low polar. It is shown that the new stationary phase is suitable for the separation of both isomers and mixtures of organic substances bearing various functional groups up to a temperature of 150°C.

Thermodynamics of solution in liquid crystalline poly(propyleneimine) dendrimers by inverse gas chromatography

Thermodynamic characteristics of infinitely diluted solutions of n-alkanes and n-alcohols in the columnar and isotropic phases of poly(propyleneimine) dendrimers, generations 1-3 (G1-G3), have been investigated by inverse gas chromatography (IGC). Effects of the dendrimer structure, the chemical nature and molecular size of the non-mesogenes on the ability to get dissolved in the liquid crystalline phases are discussed. The compatibility of the low-molecular compounds with the anisotropic phases is stated to increase with generation G.

Synthesis and Mesomorphic Properties of Substituted Pyrazinoporphyrazines

Tert-butylsubstituted pyrazinoporphyrazines (Ia–Id) and octacarboxypyrazinoporphyrazine (II) were synthesized. The structure of these compounds was determined using elemental analysis, IR and UV-Vis absorption spectroscopy. All synthesized compounds do not exhibit thermotropic mesomorphism. In this work we induced an enantiotropic mesophase due to charge transfer (CT) interactions in mixtures of compounds Ia–Id with a strong electron acceptor 2,4,7-trinitrofluorenone (TNF). The computer simulation of water systems of polar octacarboxypyrazinoporphyrazine (II) was carried out. The simulation shows that compound II does not possess mesomorphic properties in binary systems (lyotropic mesomorphism).

Mesomorphism of thermotropic poly(propyleneimine) dendrimers and phase equilibria in systems on their basis

The thermotropic mesomorphism of poly(propyleneimine) dendrimers of first, second, and third generations has been studied by the methods of polarization thermomicroscopy and DSC. Phase diagrams for the binary systems of dendrimers with n-amyloxy-n′-cyanobiphenyl calamite liquid crystal and hexa(pentyloxy)triphenylene discotic liquid crystal have been constructed. Measurements have been carried out over the entire concentration range at temperatures corresponding to the stable states of nematic, columnar, and isotropic phases. The effects of the chemical nature and shape of linear and cyclic mesogen molecules on the manifestation of mesomorphism in LC dendrimers are considered.

Thermodynamic parameters for the dissolution of n-alkanes and n-alkanols in a liquid-crystalline polypropylenimine dendrimer: A gas-chromatographic study

Thermodynamic parameters for the dissolution of n-alkanes (C7-C11) and n-alcohols (C5-C9) under infinite dilution in the columnar and isotropic phases of a polypropylenimine dendrimer have been determined by inverse gas chromatography. Thermodynamic functions have been investigated as a function of the phase state of a mesogen, the length of alkyl chains of sorbates, and temperature. For the dissolution of low-molecular-mass organic compounds, a higher endothermic effect corresponds to a larger entropy factor with its positive deviation from ideality. The dominant effect of the entropy constituent of the Gibbs energy on the dissolution of sorbates in a high-molecular-mass LC solvent has been revealed. The Rohrschneider constants have been estimated for the stationary phase based on the dendrimer. The experimental data indicate the low polarity of the sorbent that is close to those of phenyl-containing siloxane phases.

Electrostatic interactions in micellar solutions of sodium n-alkyl sulfates and applicability of the poisson-boltzmann equation for their calculation

By the example of four even members in a homologous series of sodium n-alkyl sulfates (decyl-, dodecyl-, tetradecyl-, and hexadecyl sulfate) and with the use of the Debye-Hueckel theory of strong electrolytes the parameters are calculated that determine electrostatic interactions in micellar solutions of surfactants. Calculation results for the Gibbs electrostatic energy of micellization are compared to those obtained from one of the approximate solutions of the Poisson-Boltzmann equation and also to the results of its numerical integration for spherical micelles. Applicability conditions of the Debye-Hueckel theory are determined with respect to the micelle concentration and size and the number of carbon atoms in a surfactant molecule. It is shown that the Debye-Hueckel theory in the proposed version enables an efficient and quite accurate calculation of all electrostatic properties of micelles and ionic micellar solutions for surfactants with a number of carbon atoms in a molecule starting from 10 and more and at concentrations up to 0.15 mol/dm3.

Some problems of the teaching of organic chemistry in universities of Russia

Original Russian Text

Electro-optical probe for studying local fields in organic heterostructures

Dielectric, optical, and electro-optical properties of thin Langmuir films (40–130 nm thick) of meso-substituted palladium tetraphenylporphyrin have been investigated. The key parameter of the characteristic electro-absorption band of this material—the difference in the polarizability for the excited and ground states of its molecules—has been determined. The example of determining the local field in the polymer ferroelectric in the composition of two-layer heterostructure is shown.

Design of Low-Molecular-Mass and Polymeric Discotic Mesogenes

Key directions in the molecular design of thermotropic low-molecular-mass and polymeric discotic mesogens are considered. The data on relationships between the molecular structure of disklike compounds, oligomers, and polymers formed on their basis and the manifestation of mesomorphism are generalized. Some application areas of low-molecular-mass and polymeric discotic mesogens are discussed.

The gibbs energy, chemical potential, and state parameters of the surface of an ionic micelle in the form of an ellipsoid of revolution

A molecular-thermodynamic model of an ionic micelle in the form of an ellipsoid of revolution was suggested. Equations for the chemical potential of an ellipsoidal micelle, the work of transfer of ions from solution volume into the micelle, and the state parameters of the surface of the micelle (fraction of free hydrophobic surface, surface tension coefficient, and surface charge density) were obtained. The Gibbs energy, chemical potential, work of transfer, and state parameters of an ellipsoidal micelle were determined as depending on the form factor of the corresponding ellipsoid. The model was verified for the example of sodium decyl sulfate micelles. The calculated parameters were close to the thermochemical data on the asymmetrization of spherical micelles in a solution of sodium decyl sulfate. The equilibrium ion-micellar solution composition was estimated.