Synthesis and properties of liquid crystalline poly(p-phenylene) and poly(p-phenylenevinylene) derivatives

We have synthesized poly(p-phenylene) (PPP) and poly(p-phenylenevinylene) (PPV) derivatives which are substituted with liquid crystalline (LC) groups as side chains of phenylene rings. TheLC group is composed of phenylcyclohexyl (PCH) or cyanobiphenyl (CB) moiety as a mesogenic core and various methylene spacers of 6–10. All polymers synthesized were fusible and soluble in organic solvents. PPP derivatives with the CB moiety in the LC substituent and PPV derivatives with the PCH and CB moieties in the LC substituent exhibited enantiotropic LC behaviors. The cast film of PPV derivative showed electrical conductivities of 10−5 and 10−3 S/cm before and after iodine doping, respectively. The polymer aligned by a rubbing treatment showed a linearly dichromic fluorescence.