Symmetric bent-shaped liquid crystal dimers showing transitions between optically uniaxial and biaxial smectic phases

Abstract

2015): Symmetric bent-shaped liquid crystal dimers showing transitions between optically uniaxial and biaxial smectic phases, Liquid Crystals,We report the synthesis of a new homologous series of symmetric bent-shaped liquid crystal dimers bearing oxybiphenylcarboxylate mesogens linked by a pentamethylene spacer. The dimers were characterised by optical, thermal, X-ray diffraction and computational techniques. Shorter dimers showed an I-N-SmA-SmC phase sequence with strong first-order phase transitions. For the longer dimers, the unconventional uniaxial SmA phase present in shorter members collapsed. A 9:1 binary mixture of a bent dimer with a non-mesogenic dimer exhibited upon the SmA-SmC phase transition a maximum layer contraction of 1%.

Free volume, molecular grains, self-organisation, and anisotropic entropy: machining materials

“…Plot of the nematic to isotropic liquid and the nematic to smectic A (a) and smectic C (b) phase transition temperatures (°C) [35,36]. Figure 4.…”

“…Therefore, if we compare the results for homologous materials with odd methylene parity (bent shape shown in Figure 3) with examples of some similar materials of even parity (rod-like), we find that the relationship between the liquid to nematic phase and the nematic to smectic A phase or nematic to smectic C phase transitions for the even parity materials is not linear but randomly scattered, as shown in Figure 4(a,b) [35,36].…”

Bent-core dimers with top-to-bottom linkage between central units

“…6,8,9 The same effect was proved at nonsymmetrical dimers composed of a bent-core and rod-like units. 15,[17][18][19][20][21]24 Few examples of columnar [19][20][21] and SmCP phases 22 typical for bent-shaped molecules were also found.…”

Does Introduction of a Bent Tail Stabilize Biaxiality and Lateral Switching Behavior of Smectic A Liquid Crystal Phases of Rodlike Molecules?

“…Studies regarding switching in the N b and SmA b LC phases are mostly limited to those of bent-core molecules, − disc-like molecules, − and mixtures of these molecules with rodlike molecules, − which are known to be effective. However, these core shape-assisted approaches have the problem of low electroresponsiveness due to the large excluded volume during molecular rotation.…”