Evolution of the structure of near-surface ultrahigh molecular weight polyethylene nanolayers during orientational drawing

A comparative investigation of the surface structure of ultrahigh molecular weight polyethylene film filaments obtained with different draw ratios from xerogels prepared from 1.5 wt % polymer solutions in decaline and mineral oil has been performed using a SUPRA-55V scanning electron microscope and a nanoluminograph for recording thermoluminescence of ultrathin near-surface layers of solids. It has been found that, with an increase in the draw ratio, the luminescence intensity decreases, and the peaks responsible for the segmental mobility are shifted toward higher temperatures. It has been assumed that this is associated with the improvement of the structure of near-surface layers of the polymer (with a decrease in the number of microcavities and segments of molecules with a high degree of coiling). It has also been revealed that the peaks observed in glow curves of the oriented gel samples from polymer solutions in decaline are shifted more significantly than those of the gel samples from polymer solutions in mineral oil, and the extremely oriented films are characterized by a large discretization of kinetic units of motion.     

Light-induced orientation of the molecules of nematic liquid crystals doped with comb-shaped polymers with different spatial distributions of chromophores

The orienting effect of light on nematic liquid crystals (NLCs) doped with comb-shaped polymers with different spatial distributions of side absorbing azobenzene fragments, i.e., a homopolymer (containing only azofragments), a block copolymer (containing additionally a block of non-absorbing fragments), and a statistical copolymer (containing randomly arranged absorbing and non-absorbing fragments) is experimentally studied. The light-induced Freedericksz transition threshold for the block copolymer is two times lower than that for the homopolymer. For NLC with statistical copolymer dopant, the first-order orientation transition with an extremely wide optical bistability region is observed.     

A kinetic model of thermochemical transformation of solid organic fuels

A kinetic model of thermochemical transformation of solid organic fuels was constructed. The mathematical model describes the kinetics of drying, release and combustion of volatiles, and combustion and gasification of the nonvolatile (coke) residue at linear heating. The kinetic curves of burn-out of Irsha-Borodino brown coal at various heating rates and model parameters were calculated.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1558–1567.Original Russian Text Copyright © 2004 by Boiko, Pachkovskii.     

Mass-spectrometric analysis of polymers based on furyl alcohol-polyamic acid compositions

Polymer compositions based on furyl alcohol and polyamic acid were investigated by using mass-spectrometric thermal analysis. It was established that polyamic acid catalyses both the polycondensation of furyl alcohol and the formation of a three-dimensional network of furan polymer.

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Zusammenfassung Mittels massenspektroskopischer Thermoanalyse wurden auf Furylalkohol und Polyamidsäure basierende Polymergemische untersucht. Es wurde festgestellt, daß Polyamidsäure sowohl die Polykondensation von Furylalkohol als auch die Bildung eines dreidimensionalen Furanraumnetzes katalysiert.

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