Study of oxygen transport in glassy polymers on a nanometer length scale utilizing the kinetic Monte Carlo simulations.

Diffusion-controlled deactivation of excited phenanthrene and oxidation of triplet aryl-nitrene by molecular oxygen were used to determine the energetics of oxygen jump rates in the set of glassy polymers: poly(methyl methacrylate), poly(n-butyl methacrylate), polycarbonate, polystyrene, and polysulfone. To interpret experimental results, a simple model based on the transition state theory of diffusion jump has been used. The kinetic Monte Carlo simulations of phenanthrene deactivation and nitrene oxidation were carried out in a cubic lattice that modeled a polymer matrix.

Isomerization and reorientation of Disperse Red 1 in poly(ethyl methacrylate).

Irradiation of azobenzene-containing polymer materials with light causes cis-trans isomerization and reorientation of azobenzene moieties and thereby changes in the optical properties of the materials. In this study, the film of poly(ethyl methacrylate) doped with the azobenzene derivative Disperse Red 1 (DR1) has been irradiated with the linearly polarized light of 546 nm. The time profiles of optical anisotropy and absorbance measured during irradiation have been analyzed using a kinetic model.

Wavelength Dependence of the Reorientation Efficiency of Azo Dyes in Polymer Matrixes.

Irradiation with linearly polarized light of azobenzene-containing polymeric matrixes causes reorientation of azobenzene molecules. In this study, the optical light-induced anisotropy of amorphous poly(alkyl methacrylates) doped with an azo compound was measured at different temperatures and at two irradiation wavelengths. To describe a decrease in the efficiency of anisotropy formation with temperature, a model of molecule reorientation is suggested which includes the probability of molecule reorientation per one isomerization as a basic parameter.

Study of molecular dynamics in poly(n-alkyl methacrylates) by light induced absorption anisotropy.

Formation of absorbance anisotropy under linearly polarized irradiation at 405 nm in films of poly(ethyl methacrylate) (PEMA), poly(n-butyl methacrylate) (PnBMA), and poly(n-hexyl methacrylate) (PnHexMA) doped with azo compound has been studied in a wide temperature range below Tg. The anisotropy formation kinetics has been well described under the assumption that there are two types of environments in the polymer matrixes: mobile and immobile. The mobile environment allows the dopant to reorient in the course of cis-trans-cis isomerization cycle and the immobile environment does not.

Librations of probe molecules in polymeric matrixes.

Formation of optical anisotropy under linearly polarized light has been studied in films of poly(n-butyl methacrylate) and poly(n-hexyl methacrylate) doped with azo compound (1-naphthyl-p-azo-methoxybenzene). Time profiles of the absorption anisotropy and absorbance can not be fitted with a commonly used model of anisotropy formation, which includes the transition dipole turns upon cis-trans isomerization and the rotational diffusion: the experimental values of anisotropy happen to be much lower than the calculated ones. To explain the low anisotropy level, fast molecular librations, i.

Length and time scales of structural heterogeneities in deeply supercooled propylene carbonate.

Deactivation of excited phenanthrene by molecular oxygen is utilized to probe the structural heterogeneity of supercooled propylene carbonate. The diffusion rate of oxygen molecules in different regions varies over two orders of magnitude. The size of the regions of different oxygen mobility was determined to be 1.

Length scale of heterogeneities in glassy propylene carbonate probed by oxygen diffusion.

A new method using the quenching of guest molecule phosphorescence by molecular oxygen is proposed for determination of heterogeneity size in glassy matrixes. The method is based on the high sensitivity of the diffusion of oxygen molecules to spatial density fluctuations. Phenanthrene phosphorescence decay was monitored at different concentrations of molecular oxygen in propylene carbonate below T(g).

[Sanatorium-based treatment of lumbar quadrate myofascial pain syndrome].

This paper summarizes experience gained in the Central Military Sanatorium, Sochi, in the field of diagnosis, treatment, and rehabilitation of patients with myofascial pain syndrome affecting the quadratum lumborum muscle. Conditions facilitating development of triggering myofascial structures in these muscles are analysed and methods of their diagnosis are discussed. The proposed compression test allows active trigger structures to be identified in the quadratum lumborum muscle.

Physical aging in glassy o-terphenyl monitored by probe rotation.

The physical aging of o-terphenyl was studied through its influence on the rotation rate of probe molecules (1-naphthylazomethoxybenzene) over a temperature range from 231 (T(g)-12 K) to 238.5 K (T(g)-4.5 K).

Dynamical heterogeneity in glassy o-terphenyl. 2. Measurement of environment structure lifetime using reversible reactions.

A new method is proposed for measuring the lifetime of heterogeneities in a glassy matrix. UV-vis absorption spectroscopy has been used to monitor the kinetics of photoinduced cis-->trans isomerization of 1-naphthyl-azomethoxybenzene (NAMB) in o-terphenyl (OTP) below T(g). The dependence of isomerization rate on the duration of dark interval after generation of cis molecules was established; an increase in the dark interval causes a decrease in isomerization rate.

Dynamical heterogeneity in glassy o-terphenyl: manifestation of environment changes in photoisomerization kinetics of probe molecules.

A new method for the investigation of dynamical heterogeneity in glassy matrixes is presented and illustrated by the example of o-terphenyl (OTP). UV-vis absorption spectroscopy has been used to monitor the cis-trans isomerization kinetics of probe molecules in glassy OTP. The dependence of isomerization quantum yield on light intensity has been established.

Rotational mobility of guest molecules in o-terphenyl below T(g).

An optical anisotropy decay technique for measuring probe rotational times in glassy materials is presented. Rotational times from 10(1.4) to 10(5) s have been obtained for a molecule of 1-naphthyl-azomethoxybenzene (NAMB) in o-terphenyl (OTP) over a temperature range from T(g) +3.