Molecular Alignment Structure of Dimeric Liquid Crystal Having INAC_A Phase Sequence

Abstract

Antiferroelectric liquid crystals (AFLCs) composed of low-mass mesogens do not show the nematic (N) phase. Recently, it has been reported that an AFLC containig dimeric molecules may show the N phase. However, it is not obvious why the antiferroelectric SmC (SmC_A) and N phases may coexist in the phase sequence of the dimeric LC_S. In this study, the molecular alignment structure has been researched with an X-ray diffractometer. It is found that a dimeric LC 8PY11OCB has a bookshelf structure in the SmA phase and a chevron structure in the SmC_A phase. Moreover, the molecular alignment is an intercalated structure in both Sm phases. The bent molecular structure is stable even in the SmA phase, in which the phenylpyrimidine moieties of 8PY11OCB freely rotates due to a high thermal motion with the axis being another mesogenic part including cyano group.

Keywords:

• dimeric liquid crystal
• nematic
• smectic C_A
• X-ray diffraction
• 8PY11OCB

Acknowledgments

We thank to Mr. H. Fukuro and Mr. H. Endoh of Nissan Chem. Ind. for supplying polyimide materials.