The influence of the side-arms structure on the properties of the liquid crystal dimers centred on mandelic acid

ABSTRACT

With mandelic acid (MA) as the chiral core, two series of non-symmetric liquid crystal (LC) dimers have been synthesised by changing the rigidity of the side-arms, namely the DBM-nC2B series and the DBBM-nC2B series. In the DBM-nC2B series, one side-arm is the same, while the length of the flexible tail of the other side-arm increases from 0 to 4. The same is true of the DBBM-nC2B series. Chemical structures and LC properties of the two series LC dimers were characterised by FT-IR, ¹H NMR, ¹³C NMR, DSC, TGA and POM. The results show that the DBM-nC2B series LC dimers display the nematic phase (N), and the DBBM-nC2B series LC dimers exhibit the chiral nematic phase (N*). It shows that the side-arm should have sufficient rigidity for MA to induce the N* phase. In the same series, when the length of the flexible tails of the side-arm increases from 0 to 4, it does not change the mesophase, while it has some effect on the melting temperature (T_m), the clearing temperature (T_N(*)I), and mesophase range of the dimers. The molecular length-width ratio (l/w) and dipole moment (μ) were used to explain the variation of T_m and (T_N(*)I) of LC dimer.

GRAPHICAL ABSTRACT

KEYWORDS:

• Non-symmetric liquid crystal dimers
• chiral nematic phase
• mandelic acid
• molecular conformation

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/02678292.2024.2321474.

Additional information

Funding

This work is supported by “the Fundamental Research Funds for the Central Universities” [N230020] and supported by National Training Program of Innovation and Entrepreneurship for Undergraduates [Project 202310145047].