The effect of molecular structure on mesophase behaviour of non-symmetric liquid crystal dimers containing mandelic acid and fluorine group. Issue 7 (27th May 2020)

• Record Type: Journal Article
• Authors: Chen, Xin-Shi; Xu, Zhi-Xin; Chen, Zhu; Bai, Lan-Rui; Zang, Xiang-Yu; Li, Yu-Nong; Yao, Dan-Shu; Jia, Ying-Gang; Tian, Mei
• Is Part Of: Liquid crystals. Volume 47:Issue 7(2020)
• Page Start: 1055
• Page End: 1069
• Publication Date: 2020-05-27
• Subjects: Liquid crystal dimer -- fluorinated liquid crystal -- mandelic acid -- chiral smectic A -- nematic -- chiral nematic phase; Liquid crystals -- Periodicals; 548.905
• DOI: 10.1080/02678292.2019.1704897
• Languages: English
• ISSNs: 0267-8292

Abstract

ABSTRACT: A series of non-symmetric dimers with the same chiral core, mandelic acid (MA), have been synthesised by varying the terminal group and the rigidity of the molecules, termed QBBMA-3F3BT, QBMA-3F3BT, QBMA-3F2BT, 3F3BMA-BBCN, 3F2BMA-BBCN and 3F1BMA-BBCN. Chemical structures and liquid crystal (LC) properties of the dimers were characterised by Fourier transform infrared spectroscopy, 1 H NMR, polarised optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and thermogravimetric analysis (TG). The six dimers displayed different optical activity (in THF). QBBMA-3F3BT and QBMA-3F3BT displayed enantiotropic chiral smectic A (Sm A*) phase. QBMA-3F2BT displayed N phase. The Tm of QBMA-3F3BT is the highest among QBBMA-3F3BT, QBMA-3F3BT and QBMA-3F2BT, which indicated that molecular conformation played an important role on Tm besides molecular weight and molecular rigidity. 3F3BMA-BBCN and 3F2BMA-BBCN displayed chiral nematic (N*), which indicated that the mesogenic arm BBCN is beneficial to the formation of N* phase. The LC range of 3F2BMA-BBCN is wider, which may be due to that the similar length of the two LC arms is advantageous to the interaction between C≡N group and other molecules so as to stabilise the LC phase. Graphic Abstract: uf0001