INFLUENCE OF BACKBONE RIGIDITY ON THE LIQUID CRYSTALLINITY OF MESOGEN-CONTAINING POLYACETYLENES

Two acetylene polymers containing cyanobiphenyl-based mesogens, poly{10-[((4′-cyano-4-biphenylyl)oxy)carbonyl]-1-decyne} (PA8CN), which has a relatively flexible polyalkyne backbone, and poly {[4-(((12-((4′-cyano-4-biphenylyl)oxy)dodecyl)oxy) carbonyl) phenyl]-acetylene} (PB12CN), which has a fairly rigid poly(phenylacetylene) backbone, were synthesized using respectively WCl₆ and [Rh(nbd)Cl]₂ as the catalysts. PA8CN exhibits enantiotropic interdigitated smectic A phase (S_Ad) over a temperature range as wide as ca. 100°C, whereas PB12CN is non-mesomorphic, demonstrating that the backbone rigidity plays an important role in determining the liquid crystallinity of the polyacetylenes.