Temperature Dependence Of Dynamic Behavior Research Articles

UV Biodosimeter with Visual Detection of Vitamin D Synthesis Using θ-cell

It has been shown that the LC cell, with parallel to the x-axis rubbing of a front face and circular rubbing of a rear face (θ-cell), filled with a nematic LC-805 doped by 7-Dehydrocholesterol (Provitamin D3) allows visual monitoring of the UV photoinduced conversions of Provitamin D by deviation of the disclinaton line. After an UV exposure, relaxation processes in the LC matrix result in further dark change in the deviation angle that complicates the use of θ-cell as a UV biodosimeter. Temperature dependence of dynamic behavior of the disclinaton line was investigated additionally since it is important for a UV biosensor.

Theoretical analysis of the effect of crystallization temperature on structure formation in flexible-chain polymers

Abstract Theoretical analysis of flexible-chain polymer crystallization was carried out over a wide temperature range from glass transition temperature Tg to melting temperature Tm. Temperature dependence of dynamic behavior manifesting in the decrease of crystallizing length with decreasing temperature was taken into account. The dependence of crystallizing length on temperature was obtained using chosen values of it at Tg and Tm. The crystallization with the formation of folded-chain crystals (type I) and uncoiled-chain crystals (type II) was considered. The analysis of thermodynamical favorability of both types of crystals with respect to temperature made it possible to obtain a flexible-chain crystallizing polymer phase diagram. This diagram shows the existence of two ranges where type II crystal formation is more favorable: a narrow range near Tm and the wider one near Tg, separated by the temperature range of crystallization with chain folding. Temperature dependences of type II crystals fraction in...