The effect of terminal epoxy modification on the mesomorphic and thermal stability of biphenyl ester liquid crystals

ABSTRACT

A series of biphenyl ester compounds with alkenyl, alkyl, oxirane, and 1,3-dioxolane as the terminal groups have been synthesised for investigating the mesomorphic and thermal stability. Based on the same carbon skeleton, the allyl-terminated compound V1OLC has no mesophase, while the oxirane-terminated compound POLC not only has wider multiple smectic mesophase compared with the propyl-terminated compound 3OLC but also exhibits the best thermal stability. However, when the terminal groups change from oxirane to 1,3-dioxolane, EOLC shows neither mesophase nor the good thermal stability. In addition, with the extension of the terminal chains, the butyl-terminated compound 4OLC gives the widest smectic mesophase. These imply that the mesomorphic and thermal stability of these biphenyl ester compounds are dependent on the suitable terminal chain lengths and epoxy sizes. Meanwhile, Density Functional Theory (DFT) calculations were conducted to assist in analysing the experimental results.

Graphical abstract

KEYWORDS:

• Biphenyl ester liquid crystals
• mesomorphic property
• thermal stability
• epoxy modification
• DFT calculations

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 Foundation of China (Nos. 61704133, 21673134, and 51773112), the Natural Science Foundation of Shaanxi Province (No. 2018JM6087, 2017JQ5099), the President’s Key Foundation of Xi’an Technological University (No. XAGDXJJ16001), and the Natural Science Foundation of Shaanxi Provincial Department of Education (Nos. 16JS043, 18JS051).