(S) -(-)-Ethyl Lactate as a Convenient Precursor for Synthesis of Chiral Liquid Crystals (original) (raw)

Mesomorphic and structural properties of liquid crystal possessing a chiral lactate unit

Journal of Molecular Structure, 2012

The mesomorphic and structural properties of the chiral lactic acid derivative 4 0 -(1-(octyloxy)-1-oxopropan-2-yloxy) biphenyl-4-yl 4-(decyloxy)benzoate have been studied. The compound shows the blue phase (BPII), the cholesteric (N Ã ), the TGB A and the paraelectric SmA Ã phases over a broad temperature range. Polarising optical microscopy, differential scanning calorimetry, optical transmission, X-ray diffraction and dielectric spectroscopy studies have been performed. In the SmA Ã phase the layer spacing (d) values are found to be slightly temperature dependent and suggest that there is no bi-layer association present in the mesophase. In the TGB A phase, the d values show strong temperature dependence near SmA Ã -TGB A phase transition, indicating pre-transitional effect. The temperature dependence of scattered X-ray intensities indicate the appearance of long range smectic ordering at the N Ã -TGB A phase transition. Near the TGB A -SmA Ã phase boundary strong SmA Ã fluctuations predominate. This behaviour is also observed from the temperature dependence of the d values. The transverse correlation lengths, n \ , diverge near the N Ã -TGB A phase transition indicating second order phase transition.

Review Chiral Liquid Crystals: Structures, Phases, Effects

2014

The introduction of chirality, i.e., the lack of mirror symmetry, has a profound effect on liquid crystals, not only on the molecular scale but also on the supermolecular scale and phase. I review these effects, which are related to the formation of supermolecular helicity, the occurrence of novel thermodynamic phases, as well as electro-optic effects which can only be observed in chiral liquid crystalline materials. In particular, I will discuss the formation of helical superstructures in cholesteric, Twist Grain Boundary and ferroelectric phases. As examples for the occurrence of novel phases the Blue Phases and Twist Grain Boundary phases are introduced. Chirality related effects are demonstrated through the occurrence of ferroelectricity in both thermotropic as well as lyotropic liquid crystals. Lack of mirror symmetry is also discussed briefly for some biopolymers such as cellulose and DNA, together with its influence on liquid crystalline behavior.