Title:Synthesis and Mesomorphic Properties of New Non-symmetric Liquid
Crystal Dimers
Volume: 20
Issue: 7
Author(s): Chi-Kien Seou, Sie-Tiong Ha*, Yip-Foo Win and Guan-Yeow Yeap
Affiliation:
- Department of Chemical Science, Faculty of Science, Universiti Tunku Abdul Rahman, Jln Universiti, Bandar Barat,
Kampar, 31900 Perak, Malaysia
Keywords:
liquid crystal, dimer, benzothiazole, benzylideneaniline, nematic, lateral.
Abstract: New non-symmetric liquid crystal dimers, N-(4-(n-(4-(benzothiazol-2-yl)phenoxy) alkyloxy)
benzylidene)-2,4-difluoroaniline (DSFCn), containing two mesogenic core units of benzothiazole
and benzylideneaniline were reported. The core system was connected by a flexible alkyl spacer,
-(CH2)n-(where n =2-6, 8, 10, and 12). The spectroscopic techniques were employed to confirm the
molecular structure of the title compounds. Differential scanning calorimetry and polarizing optical
microscopy were used to study the mesomorphic properties of the synthesized compounds. Observation
under crossed polarized light reveals that compounds (n = 4, 5, 6, 8, 10, 12) are purely nematogens.
The nematic phase in the dimers are caused by the presence of the lateral fluorine atoms at the
benzylideneaniline core. Mesophase thermal stability has been suppressed significantly by the fluorine
atom at the lateral position which increased the molecular breadth and subsequently, results in weaker
overall lateral intermolecular attraction. The structure-property relationships of the dimers were inferred
through comparison of thermal properties of the present dimers with those of the earlier reported
analogous that do not possess any lateral substituents.
