Thermal and optical properties of amphitropic liquid crystals derived from cholesterol and cinnamic acid

ABSTRACT

In this paper, we firstly demonstrate the synthesis of chiral amphitropic liquid crystals derived from cholesterol as well as their thermal and optical properties. Chiral monomeric cholesteryl-4-(6-acryloyloxyhexyloxy) cinnamate (CCM) derived from cholesterol and cinnamic acid has been synthesised showing amphitropic liquid crystal phases. The synthesised CCM exhibits oily streak textures under a polarised optical microscope (POM), corresponding to cholesteric liquid crystal phase formed after heating over 120°C and after being treated with organic solvents such as dichloromethane, chloroform, tetrahydrofuran and toluene. Both the thermotropic and lyotropic cholesteric liquid crystals exhibit selective light reflection, and the wavelength of the reflected light falls in the visible light region showing colourful appearances. The results suggest that CCM could be used for the development of sensors for both temperature and solvents. Homopolymer (Poly-CCM) was synthesised via free radical polymerisation. The synthesised polymer did not exhibit any mesomorphic behaviour either by heating or being treated with solvents. These results indicate that the long chain hydrocarbons and sidechains of CCM were disturbed and restricted after polymerisation leading to the loss of liquid crystalline properties. However, cholesteric construction of monomeric CCM was fixed via UV-polymerisation. The synthesised Poly-CCM film shows Bragg reflection significantly.

Graphical abstract

KEYWORDS:

• Cholesteric liquid crystals
• lyotropic
• thermotropic
• amphitropic
• Bragg reflection

Acknowledgments

The authors would like to thank the Ministry of Science and Technology (MOST) of the Republic of China (Taiwan) for financially supporting this research under Contract MOST 107-2221-E-006-071.

Author contributions

Yi-Hua Hung and Wei-Chieh Chen performed the experiments and statistical analyses of the data. All of them are graduated students in our research lab. Jui-Hsiang Liu wrote the original manuscript, with edits by Chun-Yen Liu, and reviewed by all authors. Jui-Hisang Liu and Chun-Yen Liu supervised the whole project. Currently, both of them are professors at National Cheng Kung University. Their research interests are Synthesis and Characterization of Liquid crystals and fabrication of polymer actuators using liquid crystal elastic polymers.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data and materials availability

All data and materials described in this manuscript are available.

Supplementary material

Supplementary data for this article can be accessed here.

Additional information

Funding

This work was supported by the Ministry of Science and Technology, Taiwan [MOST 107-2221-E-006-071].