Crystal Research and Technology
Cryst. Res. Technol. 41, 914 (2006) - Abstract -

Phase transition behavior and structure of the thermotropic liquid crystal 6-{[(4’-{[(undecyl)carbonyl]oxy}biphenyl-4yl)carbonyl]oxy}-1-hexyne

Leijing Liu, Jianxin Geng, Junliang Yang, Gao Li, Enle Zhou, Jacky Wing Yip Lam*, and Benzhong Tang*

State Key Laboratory of Polymer Physics and Chemistry, Changchun Inst. of Appl. Chem., Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Changchun, 130022, China
*Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

Keywords thermotropic liquid crystal, phase transition, structure, metastable
PACS 64.70.Md
DOI 10.1002/crat.200510695

The phase transition behaviors and corresponding structures of 6-{[(4’-{[(undecyl)carbonyl]oxy}biphenyl-4yl)carbonyl]oxy}-1-hexyne (A4EE11) were investigated using differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and wide angle X-ray diffraction (WAXD). In comparison with the published homologues, 5-{[(4’-heptoxy-biphenyl-4-yl)carbonyl]oxy}-1-pentyne (A3EO7) which shows a monotropic smectic A (SmA) phase and a metastable monotropic smectic C (SmC) phase; 5-{[(4’-heptoxy-biphenyl-4-yl)oxy]carbonyl}- 1-pentyne (A3E’O7) that exhibits three enantiotropic stable liquid crystalline (LC) phases, SmA phase, SmC phase and smectic X (SmX) phase; 5-{[(4’-heptoxy-biphenyl-4-yl)carbonyl]oxy}-1-undecyne (A9EO7) which has a monotropic SmA phase and a metastable crystal phase, A4EE11 integrates the enantiotropy, monotropy and metastability of the LC phases of those three compounds. Upon cooling from isotropic state to room temperature, in the temperature range of 62.0 to 58.5°C, A4EE11 shows an enantiotropic smectic A (SmA) phase with a layer spacing d=32.69Å. Further lowering the temperature, it enters into a metastable monotropic smectic B (SmB) phase with a longer layer spacing d=34.22Å which has a tendency towards crystallization. The metastability of the liquid crystalline phase may associate to the linkage order of the ester bridge between the mesogenic core and the flexible spacer.




The full text of this paper in pdf-Format:

If you have come directly to this page, click this symbol to go to the CRT homepage.