Dielectric properties to 3 GHz of liquid crystal mixtures andseveral alcohols by time domain reflectometry

摘要

Studies have been made of the complex dielectric permittivities ofmixtures of cholesteric liquid crystals and of a homologous series ofnormal alcohols. The dielectric spectroscopy was done by the method oftime-domain reflectometry (TDR). The liquid crystals were cholesterylalkanoates with cholesteric-isotropic transition temperatures of19° C and 72° C. The 50 weight percent mixture hasT_CI=32° C. This transition was investigated by TDR. In thecase of the alcohols a simple quantum model has been developed toexplain a systematic variation of the dielectric loss peaks versusmolecular length. A comparison with experimental data indicates that allof the alcohols studied (up to C₁₂H₂₅OH,dodecanol) behave as fully extended molecules at the temperature atwhich librational motion goes over into rotation