Influence of chiral monomer concentration on thermo-optical properties of glass-forming cyclic siloxane side chain liquid crystal oligomers

ABSTRACT

A series of new cyclic siloxane side-chain liquid crystal oligomers containing chiral (-)-menthyl monomer (M₁) and achiral benzene methyl ester monomer (M₂), denoted as O₁–O₄, were successfully synthesised. Their chemical structures were confirmed by FT-IR and ¹H NMR spectra. Phase transition behaviours and phase structures were investigated by differential scanning calorimetry (DSC) and polarised optical microscopy (POM). Bragg-selective reflection spectra were measured by ultraviolet/visible spectrometer (UV/Vis). The glassy oligomers with bright colours at room temperature were obtained by thermal quenching treatment with liquid nitrogen (liquid Nr). The reflection colours were adjusted into visible light region by adjusting the chiral monomer content (X_M1*) in oligomers. The glassy oligomers have shown good thermal stability at room temperature for more than 1 year.

Graphical abstract

KEYWORDS:

• Cyclic side-chain liquid crystal oligomers
• glassy state
• chiral monomer concentration
• thermal-optical properties

Disclosure of potential conflicts of interest

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

Additional information

Funding

This work was supported by the Natural Science Foundation of Jiangsu Province [BK20190157]. Natural Science Foundation of the Jiangsu Higher Education Institutions of China [19KJB430038]. National Nature Science Foundation of China [21861040], Fujian Natural Science Foundation [2019J0106], and Scientific Research Fund project of Ningde Normal University [2020Z02, 2018Y06, 2018T02].