Viscous Properties of Nematic Mixture at Variation of PVT-State Parameters

Abstract

The results of acoustic investigations of the viscous properties of a nematic liquid crystal mixture with wide temperature range at varying PVT-state parameters are presented. The original ultrasonic set-up was elaborated to provide the determination of some dissipative parameters including the ratio of twist viscosity c 1 to magnetic susceptibility anisotropy Dv as a function of pressure (P) and temperature (T) at constant volume ( V ). It is found that the ratio c 1 =Dv exponentially decreases with increasing temperature or with decreasing pressure. This agrees with the free volume theory. According to our calculation free volume increases with temperature or decreasing pressure. The energies of activation (E v , E p ) of the twist viscosity at constant volume and pressure are calculated. The dependence of Leslie viscosity coefficient a 1 on temperature is determined too.

Ultrasound in Liquid Crystals

“…A lot of ultrasonic investigations of liquid crystals in rotating magnetic fields conducted so far [6,[20][21][22] confirm this conclusion. A lot of ultrasonic investigations of liquid crystals in rotating magnetic fields conducted so far [6,[20][21][22] confirm this conclusion.…”

“…A number of investigations confirm this conclusion [6,[20][21][22]. A number of investigations confirm this conclusion [6,[20][21][22].…”

“…Such an attempt was made in the work [20] for a nematic mixture ZhK440 (2 : 1 mixture of p-n-butyl-p-methoxyazoxybenzene and n-butyl-pheptanoyloxyazoxybenzene). Such an attempt was made in the work [20] for a nematic mixture ZhK440 (2 : 1 mixture of p-n-butyl-p-methoxyazoxybenzene and n-butyl-pheptanoyloxyazoxybenzene).…”

Influence of P, V, T – Termodynamic State Parameters upon Dynamics of Orientational Processes of Nematic Liquid Crystals

“…Для исключения указанного недостатка разработана двухканальная акустическая камера (рис. 1) [5], расположенная в автоклаве, корпус 2 котороой изготовлен из диа-магнитной нержавеющей стали марки 10Х17Н13М2Т и способен выдерживать давления до 1,2·10…”

“…Поэтому данный канал используется для определения ско-рости ультразвука. Под действием давления рас-стояние ℓ 2 между излучающим пьезоэлементом 8 и принимающим пьезоэлементом 5 изменяется, что используется для измерения плотности [5]. Элек-трический сигнал подается в измерительную каме-ру с помощью высокочастотных кабелей, проло-женных в трубке высокого давления 1.…”