Abstract
Liquid crystals formed by acute-angle bent-core (ABC) molecules with a 1,7 naphthalene central core show an intriguing phase behavior with the nematic phase accompanied by poorly understood additional phases. In this work, we characterize the physical properties of an ABC material, such as birefringence, dielectric permittivities, elastic constants, and surface alignment, and present X-ray diffraction and transmission electron microscopy studies of their ordering. The ABC molecular shape resembling the letter $\lambda$ yields a very small splay elastic constant in the uniaxial nematic phase and results in the formation of a tetragonal positionally ordered columnar phase consisting of molecular columns with a uniform uniaxial director that can be bent but not splayed.
Highlights
The molecular shape is a key factor responsible for physical properties of liquid crystals
The phase diagram obtained by polarizing optical microscopy (POM) textural observations is shown in Fig. 2, which is consistent with the differential scanning calorimetry (DSC) data in Ref. [18]
The mesomorphism of angle bent core (ABC)-compounds with a 1,7naphthalene central core was reported by Lee et al [46]
Summary
The molecular shape is a key factor responsible for physical properties of liquid crystals. The simplest rodlike molecules produce a uniaxial nematic (N), widely used in applications. There has been much interest in the socalled bent core molecules, formed by two rodlike segments attached to each other at some angle β. This kinked shape leads to fundamentally different properties and phases, as reviewed recently [1,2]. The molecule is formed by two arms attached in an asymmetric fashion to the central 1,7-naphthalene core. It produces a high-temperature uniaxial N and a low-temperature
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