UNIQUE LIQUID-CRYSTALLINE BEHAVIOR OF CONDUCTING POLYACETYLENE DERIVATIVES

Unique liquid crystalline behaviors have been observed in polyacetylen e derivatives substituted with long side chains containing mesogen uni t such as poly 4'-n-octylcyclohexyl)phenoxy)-1-pentyne](PPCH803A) with phenylcyclohexyl mesogenic moiety. Texture typical to smectic liquid crystal has been confirmed by optical microscopic observation. Smectic structure has also been confirmed by X-ray diffraction. Anisotropy of optical absorption spectrum consistent with X-ray diffraction has bee n observed, from which the band gap of PPCH803A has also been evaluate d to be 2.7 eV. Dielectric constant of PPCH803A in the smectic phase ( 90-150 degrees C) is about 2.8 and changes at phase transition tempera ture in step wise. The mixture of PPCH803A with ferroelectric liquid c rystal of low molecular weight exhibits large dielectric constant and unique ferroelectric behavior in the temperature range of the smectic phase of PPCH803A.