Heterogeneous equilibria and the kinetics of isotropic liquid-nematic phase transition in a multicomponent mixture 4-alkyl-4′-cyanobiphenyls

The isotropic liquid-nematic phase transition and the kinetics of growth of nematic phase drops during this phase transition were studied by polarization optical microscopy and IR spectroscopy for a four-component system during cooling. The statistical drop size distribution was described in terms of the equilibrium thermodynamics of irreversible processes. An analysis of the time dependences of the mean diameter of drops showed the presence of two kinetic stages of nematic phase growth and allowed them to be described by the universal law of cluster growth. In conformity with the Gibbs phase rule, nematic phases with different compositions can coexist at equilibrium.     

Scale effect of Young's modulus of highly oriented polymers

The scale effect of the acoustic Young's modulus E of oriented polymer fibers has been experimentally revealed. If the fiber length L is smaller than its critical value L₀, the modulus decreases proportionally to the logarithm of the fiber length. An increasing temperature causes a proportional increase in the slope dE/d(In L). The scale effect is explained by the influence of the specimen volume on the probability of initiation of intense thermal fluctuations, which cause a decline in the Young's modulus.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 6, pp. 839–846, November–December, 1998.     

Statistical Analysis of the Microstructure and Mechanical Properties of Rolivsans in the Course of Thermal Curing

The reversible aggregation model was applied to analyze the electron-microscopic data for statistical ensembles of Rolivsan microdomains in the course of thermal curing. The experimentally established correlation between the average size of the microdomains in the ensembles and the dynamic Young modulus of the Rolivsan samples cured at different temperatures was interpreted in terms of the kinetic strength concept.     

Particle-Size Distribution of Wood Resin and Sulfate Lignin in Aqueous Alkaline Solution

Particle-size distribution of wood resin, sulfate lignin, and their mixtures in aqueous alkaline solutions (pH 12.7) at 293–333 K was described in the framework of the thermodynamic model. The increase in the average particle size and the broadening of the distribution are caused by an increase in the energy of thermodynamic fluctuations.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 498–501.Original Russian Text Copyright © 2005 by Bronnikov, Dem’yantseva.     

The oxidative polymerization of aniline as topochemical process. The statistical analysis of grain growth

The films of polyaniline (PANI) on the glass slides with granular morphology were prepared by oxidative polymerization with ammonium peroxydisulfate in strong acidic conditions. The kinetics of polymerization was monitored recording of scanning electron microscopy images of deposit PANI films on glass slides. Statistical analysis of the PANI grain size was successfully applied for characterization of the polymerization process. It was shown that oxidative PANI polymerization could be described as a topochemical process. This allowed us explaining the existence of three phase of process (induction period, acceleration stage and decay) and finding the kinetics parameters of these stages. The model of phenazine nucleates was used to described induction stage. It was shown that phenazine nucleation process can be described kinetically as zero-order reaction. The acceleration stage of PANI polymerization was connected with increase of PANI grain surface during reaction and the mechanism of this acceleration was discussed. The decay stage of process was attributed with formation fuse loose PANI film with reduced available interphase surface for polymerization process.     

Dielectric properties of liquid-crystal azomethine polymer with alkyl-substituted side chain

Physics of the Solid State - Relaxation processes in side-chain liquid-crystal azomethine polymer have been studied using dielectric spectroscopy in wide ranges of temperatures and frequencies. Two...     

Regular phantom black holes

We study self-gravitating, static, spherically symmetric phantom scalar fields with arbitrary potentials (favored by cosmological observations) and single out 16 classes of possible regular configurations with flat, de Sitter, and anti-de Sitter asymptotics. Among them are traversable wormholes, bouncing Kantowski-Sachs (KS) cosmologies, and asymptotically flat black holes (BHs). A regular BH has a Schwarzschild-like causal structure, but the singularity is replaced by a de Sitter infinity, giving a hypothetic BH explorer a chance to survive. It also looks possible that our Universe has originated in a phantom-dominated collapse in another universe, with KS expansion and isotropization after crossing the horizon. Explicit examples of regular solutions are built and discussed. Possible generalizations include k-essence type scalar fields (with a potential) and scalar-tensor gravity.     

Some exact models for nonspherical collapse. III

The gravitational nonradiative collapse of dust configurations in the presence of electromagnetic field is analyzed in terms of exact dynamical solutions for a wide range of spacetime symmetries: cylindrical, pseudoplanar, toroidal, and also spherical, planar, and pseudospherical [when the anisotropy factor of the (x ²,x ³) surfaces,(R, T), is replaced by a massless scalar field]. The condition that the collapse is nonradiative leaves three possibilities for the coordinate dependence of(R,T) (i)=(a),a (R, T) being the scale factor of the (x ²,x ³) surfaces, (ii)=(T), and (iii)=(R). Almost all (in the meaning indicated in the text) solutions for charged dust with=(a) and for dust in the external electromagnetic field with=(T) and=(R) have been obtained and discussed. A wideranging discussion concerning the topics of papers I–III is given. Special attention is paid to the question of horizon existence and formation and also the perspective of extension of the techniques developed onto the more realistic case of axial symmetry.     

A statistical study of the kinetics of phase separation for a liquid crystalline mixture

The kinetics of cholesteric phase growth during the phase separation of an isotropic liquid crystalline mixture was studied by polarizing optical microscopy within the framework of the thermodynamics of irreversible processes. The rules governing time-dependent changes in the parameters of the statistical droplet size distribution of the cholesteric phase were determined. The influence of the thickness of the liquid crystalline mixture layer on the size of the droplets formed was studied.