Orientational and Conformational Characteristics of Oxyethylene-Type Spacers Involved in Dimer Liquid Crystals

Thermodynamic Characteristics of Chain Molecules in the Nematic State: PVT Studies of Main-Chain Liquid Crystal Comprising a Long Oxyethylene-Type Spacer

“…Results of the conformational analysis suggest that similar arguments apply to the phase behaviors of MBBE-6. 25 The concept of the nematic phase described above is schematically illustrated in Figure 7. The conformational ordering of chain segments in the nematic state has also been investigated by other research groups.…”

“…Orientational characteristics of the sample in the LC state were investigated by the 2 H NMR method, and the variation of the order parameter with temperature has already been reported. 25,26 A PVT apparatus manufactured by GNOMIX Co. was used to determine the change in specific volume as a function of temperature and pressure. Measurements were carried out in the isothermal mode; volume readings were recorded over a pressure range from 10 to 100 MPa at a fixed interval (10 MPa) while the temperature was kept invariant.…”

“…24 More recently, the preparation and the preliminary results of spectroscopic studies of dimer LCs (called MBBE-x with x ) 2-6) have been reported. 25 The phase transition temperatures of MBBE-x (x ) 2-9) have been determined by DSC and are indicated in Chart 1. 26 The number of atoms involved in the spacer increases in † Tokyo Polytechnic University.…”

Twin liquid crystals and segmented thermotropic polyesters containing azobenzene—effect of spacer length on LC properties

“…The reason for this being the interesting “odd–even” oscillation observed in the isotropization temperatures and entropies as a function of the even or odd parity of the number of atoms in the methylene spacer length 18, 21. Conversely, the poly(oxyethylene) units preferred a “gauche” conformation and the twins with poly(oxyethylene) central spacer generally did not show odd–even oscillation of the isotropic‐LC transition entropy 22, 23. In the design of our azobenzene twin molecules, the choice of oligooxyethylene as the central spacer was very important, as it served two purposes, first, it reduced the melting transition of the resulting twin molecules so that melt polycondensation route could be adopted, and second, it improved their solubility considerably.…”

“…poly(oxyethylene) central spacer generally did not show oddeven oscillation of the isotropic-LC transition entropy. 22,23 In the design of our azobenzene twin molecules, the choice of oligooxyethylene as the central spacer was very important, as it served two purposes, first, it reduced the melting transition of the resulting twin molecules so that melt polycondensation route could be adopted, and second, it improved their solubility considerably. Another important aspect was that the polar oligooxyethylene spacer units are usually incompatible with the rigid rod-like azobenzene mesogen resulting in segregation into separate domains leading to mesophase formation.…”