Synthesis, Characterization, and Electro-Optic Properties of Novel Bent-Core Mesogens Based on Cinnamoyloxy Derivatives

Abstract

The new series of bent-core molecules based on a 3,4′-biphenyldiol central core has been synthesized. The influence of the central core as well as that of a fluorine and chlorine substituent on the diphenyl rings in the bent-core compound has also been examined. A few novel series of bent-core compounds containing cinnamoyloxy or α-methylcinnamoyloxy groups in the side arms have been synthesized, and the mesophases exhibited by them have been compared. The mesophases under discussion were investigated by means of polarizing microscopy, differential scanning calorimetry, X-ray diffraction, as well as electro-optical experiments. The influence of the molecular structure on the occurrence of the SmCP phase was investigated. Finally, the electro-optical properties of the SmCP phase, such as voltage-transmittance effect, tilt angle, dielectric permittivity, and switching behavior, were also measured. As a consequence, the correlation between their electro-optical properties and chemical structures of these compounds is investigated.

Keywords:

• Bent-core mesogens
• cinnamoyloxy
• dielectric permittivity
• tilt angle
• voltage-transmittanceeffect

Acknowledgment

We thank Dr. Jey-Jau Lee for help with the XRD experiments at theNational Synchrotron Radiation Research Center (NSRRC, for the beamline BL17A) in Taiwan. Financial support from the National Science Council of Taiwan (ROC) through NSC 98-2221-E-011-004 is gratefully acknowledged.

Notes

^a Abbreviations: Cr = crystalline phase; SmCP = polar SmC phase (i.e., B₂ phase); I = isotropic phase (• = phase exists).

^a The data were measured in the range T_C – T = 15°C.