Preparation, structure and optical properties of thermochromic liquid crystal compounds containing (−)-menthyl with selective reflection

• Published in: Journal of molecular liquids 2019-02, Vol.275, p.241-250
• Main Authors: Luo, Cong-Cong, Wang, Xin-Jiao, Han, Lu-Juan, Jia, Ying-Gang, Ying, Shao-Ming, Wang, Ji-Wei
• Format: Article
• Language: English
• Subjects: (−)-Menthol; Blue phase; Chiral liquid crystals; Chiral smectic C; Selective reflection; Thermochromic
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2018.11.088

A series of new chiral liquid crystal compounds named MOPnB containing (−)-menthyl group has been prepared and characterized by FT-IR and 1H NMR spectra. The thermal properties and optical textures were investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Increasing the length of the terminal alkoxy group tended to decrease the clearing points and narrow the temperature range of the N* phase as well as favored the development of SmC* phase. Furthermore, Bragg selective reflection spectra of the compounds were measured by ultraviolet/visible spectrometer (UV/Vis). All compounds MOPnB (n = 2, 4, 6, 8, 10) revealed the thermochromic property or selective reflection of visible light in the N* phase. Additionally, only MOP10B and MOP12B in the SmC* phase had the thermochromic phenomena and gave red-saffron colour. [Display omitted] •Novel CLCs MOPnB based on (−)-menthol with high chirality were synthesized.•All chiral liquid crystals MOPnB displayed blue phase.•MOPnB (n = 2–10) revealed the thermochromic property in N* phase on heating.•MOPnB (n = 10, 12) revealed the thermochromic property in SmC* phase on cooling.