Freedericksz Transition Studies of Solutions of Side Chain Polymer Liquid Crystals in Low Molar Mass Mesogens

Abstract

A series of side chain liquid crystal polymer solutions using a low molar mass mesogen as the solvent have been studied by optical microscopy, the Freedericksz transition and dielectric constant measurements. The optical microscopy was used to establish that all the solutions were nematic and to determine their phase transitions. The samples were aligned homeotropically or with a planar texture and Freedericksz transition measurements were carried out using magnetic and electric fields. The apparatus and method used are described in detail. The dielectric constants were determined using a capacitance bridge method. From these measurements it was established that k₁₁, k₃₃, k₃₃/k₁₁ and δ∈ all decrease with increasing polymer concentration. The maximum polymer concentration used was 19.5% w/w and all the solutions were stable and homogeneous. It was also shown that the polymer appears to decrease the amount of antiparallel ordering exhibited by the cyano terminated nematogens. The results are discussed in terms of the important polymer features.