Unique electrical and optical properties of polyacetylene derivatives in liquid crystal phase

Polyacetylene derivatives substituted with long side chains containing mesogen unit such as poly[5-(p-(trans-4′-n-alkylcyclohexyl)phenoxy)-1-alkyne] (PPCHn0mA) exhibit unique liquid crystalline behavior. Typical microscopic texture and sharp X-ray diffraction peak have been confirmed, which is characterictic of the smectic-A phase of liquid crystal. Anisotropy of optical absorption spectrum has been observed, from which the band gap of PPCH803A has also been evaluated to be 2.7 eV. Dielectric constant of PPCH803A increases in the smectic phase. It is also found that the ferroelectricity is induced in the temperature range of the smectic phase of PPCH803 by mixing with PPCH803A ferroelectric liquid crystal of low molecular weight.