Nonlinear elasticity and friction of liquid-crystalline polymer monolayers

In the present paper we consider nonlinear elasticity and friction of grafted persistent chains, which are highly stretched in the normal to the surface direction due to orientational interactions. We examine the normal and the lateral forces both in equilibrium and under shear sliding when the monolayer is confined by a bare surface. We show that in the confined monolayer in equilibrium the tilted orientation of the director becomes stable. In the sliding regime the friction force passes through a maximum value. The additional normal force in the sliding regime, when the distance between the surfaces is fixed, is also considered. We show that this force is attractive for small velocities and becomes repulsive for high velocities after the friction force passes through the maximum value

Эффективность дорназы альфа (пульмозим) у детей с хроническими заболеваниями легких

Effect of Pulmozyme is studied in 28 children aged 8 to 16 with chronic lung diseases (14 children with congenital bronchi defects, 6 ones with the Kartagener's syndrome, 2 ones with hypogammaglobulinemia, 6 ones with chronic pneumonia). The drug was given in the dose of 2.5 mg once a day by inhalation. The treatment course was 10 days. Eight children received endobronchial Pulmozyme during bronchoscopic procedure. The sputum viscosity was tested with a rotary viscometer Reotest 2.1 (Germany) using a cone — flat working joint under the standard temperature of 20°C.The Pulmozyme therapy caused a positive clinical dynamics in all the children such as easier sputum expectoration due to reduction of its viscosity resulted in more effective bronchial drainage and improvement in the patients' general status. The study in vitro showed Pulmozyme to diminish the sputum viscosity and structuring from 104 to 103—102 mPa/s; the mucolytic effect of Pulmozyme kept for a day. The sputum viscosity in vitro was investigated before the drug inhalation, just after and in 4 and 8 hrs. The maximal viscosity decrease from 104 to 103—102 mPa/s was found 4 hrs after the inhalation followed by the viscosity growth up to the initial level 8 hrs after the inhalation. The adverse effect of Pulmozyme was noted in 1 patient (sore throat). The endobronchial delivery provided fast mucolytic effect and an improved expectoration after the bronchoscopic procedure.Действие пульмозима исследовано у 28 детей в возрасте от 8 до 16 лет с хроническими заболеваниями легких (14 детей с врожденными пороками развития бронхов, 6 с синдромом Картагенера, 2 с гипогаммаглобулинемией, 6 с хронической пневмонией). Препарат назначался в дозе 2,5 мг в ингаляции 1 раз в сутки. Курс лечения составлял 10 дней. 8 детям пульмозим вводился эндобронхиально при бронхоскопии. Вязкость мокроты исследована на ротационном вискозиметре Реотест 2.1 (Германия) с использованием рабочего узла конус-плоскость при стандартной температуре 20°С.На фоне лечения пульмозимом у всех больных была отмечена положительная клиническая динамика, выражавшаяся в легком откашливании мокроты за счет уменьшения ее вязкости, что приводило к эффективному дренажу трахеобронхиального дерева и улучшало общее состояние пациентов. При исследованиях in vitro показано, что добавление пульмозима приводит к снижению вязкости и степени структурирования мокроты с 104 до 103— 102 мПа/с; муколитический эффект пульмозима сохраняется в течение суток. In vivo вязкость мокроты исследована до ингаляции, сразу после и через 4 и 8 ч. Максимальное снижение вязкости с 104 до 103—102 мПа/с отмечено через 4 ч после ингаляции с последующим нарастанием вязкости практически до исходного уровня через 8 ч после ингаляции. Побочный эффект отмечены у 1 больного (першение в горле). При эндобронхиальном введении отмечен быстрый муколитический эффект и улучшение экспекторации после бронхоскопии

Self-Organization of Polymeric Fluids in Strong Stress Fields

Analysis of literature data and our own experimental observations have led to the conclusion that, at high deformation rates, viscoelastic liquids come to behave as rubbery materials, with strong domination by elastic deformations over flow. This can be regarded as a deformation-induced fluid-to-rubbery transition. This transition is accompanied by elastic instability, which can lead to the formation of regular structures. So, a general explanation for these effects requires the treatment of viscoelastic liquids beyond critical deformation rates as rubbery media. Behaviouristic modeling of their behaviour is based on a new concept, which considers the medium as consisting of discrete elastic elements. Such a type of modeling introduces a set of discrete rotators settled on a lattice with two modes of elastic interaction. The first of these is their transformation from spherical to ellipsoidal shapes and orientation in an external field. The second is elastic collisions between rotators. Computer calculations have demonstrated that this discrete model correctly describes the observed structural effects, eventually resulting in a “chaos-to-order” transformation. These predictions correspond to real-world experimental data obtained under different modes of deformation. We presume that the developed concept can play a central role in understanding strong nonlinear effects in the rheology of viscoelastic liquids

Rheology of polysulfone-N-methylpyrrolidone solutions used in the technology of lithium-ion batteries

This paper is devoted to the analysis of the rheological properties of polysulfone solutions in N-methylpyrrolidone, which are an intermediate stage in preparing lithium-ionic batteries. The viscosity of the solutions has been measured in wide ranges of shear rate, temperature, and concentration. The crucial role of water in measuring the rheological properties of solutions has been observed and avoided. The solutions under study are Newtonian liquids, but they demonstrate the elasticity at moderately high concentrations. The concentration dependence of viscosity is very strong, and the threshold was found where the viscosity grows unlimitedly due to the transition of the solution to the gel-like state. Temperature dependences of viscosity are described by the Arrhenius-type equation with the activation energy increasing along with an increase in the polymer concentration in solutions

Synthesis and Characterization of Novel Wholly Aromatic Copolyesters Based on 4′-Hydroxybiphenyl-3-Carboxylic and 3-Hydroxybenzoic Acids

A series of new wholly aromatic (co)polyesters based on m-substituted bifunctional comonomers—4′-hydroxybiphenyl-3-carboxylic (3HBCA) and 3-hydroxybenzoic (3HBA) acids with molar ratios of 3HBCA:3HBA from 0:100 to 60:40, respectively—was synthesized. NMR and FTIR spectroscopy methods proved the full compliance of the copolymer composition with the target ratio of comonomers, as well as high compositional homogeneity (absence of block sequences). The resulting copolyesters have a sufficiently high molecular weight and their intrinsic viscosity values are in the range of 0.6–0.8 dL/g. Thermal analysis showed that all 3HBCA-3HBA copolyesters are amorphous, and with an increase in the content of biphenyl units (3HBCA), the glass transition temperature increases significantly (up to 190 °C). The onset of the intense thermal decomposition of the synthesized polyesters occurs above 450 °C. Thus, this indicates a sufficiently high thermal stability of these polyesters. Rheological measurements have shown that melts of copolyesters with a high content of 3HBCA units exhibit anisotropic properties. At the same time, the method of polarization optical microscopy did not confirm the transition to the liquid crystal state for these polyesters. These results confirm that it is possible to obtain high-performance polyesters based on 3HBCA, but not a mesogenic comonomer. Thus, 3HBCA is a promising comonomer for the synthesis of new thermotropic copolyesters with controlled anisotropic properties