Synthesis and properties of new non-symmetric liquid crystal dimers containing mandelic acid and cyano group

ABSTRACT

Four non-symmetric dimers containing mandelic acid as the chiral core have been synthesised, termed as QBMA-B, QBMA-BCN, QBMA-BBCN and QBBMA-BBCN, respectively. Chemical structures and liquid crystal (LC) properties of the dimers were characterised by FTIR, ¹H-NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and polarised optical microscopy (POM). The results indicated that the rigidity and conformation of the molecules of the dimers played important effects on their mesophase properties. QBMA-B did not display any mesophase, QBMA-BCN and QBMA-BBCN exhibited nematic (N) phases, while QBBMA-BBCN displayed cholesteric (ch) phase, which indicated that chiral mandelic acid could induce cholesteric phase, but some attention should be paid to the molecular conformation to obtain cholesteric phase. For the four dimers, melting temperature (T_m) increased first and then decreased, inferring that molecular conformation played a more important effect besides molecular weight and rigidity.

Graphical Abstract

KEYWORDS:

• Mandelic acid
• semi-flexible spacer
• nematic
• cholesteric phase
• cyano group

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by the National Natural Science Fund of China [Grant Number 51273035], and the Fundamental Research Funds for the Central Universities [Grant Number N160504001].