Synthesis and properties of thermotropic liquid‐crystalline polymers linked through bis(ß‐diketonato)copper(II) complex

Thermotropic liquid‐crystalline polymers (2a–2e, 3a–3c) linked via the bis(ß‐diketonato)‐copper(II) complex were prepared by mixing the bifunctional bidentate ligand (1a–1c) with copper(II) chloride. The homopolymers 2c–2e and the copolymers 2a–3c were ascertained to exhibit a stable mesophase by means of polarizing microscopic observation. The homopolymers show at least a smectic mesophase and the copolymer exhibit both smectic and nematic ones. Fibers were prepared by melt‐drawing of the molten polymers at the mesophase temperature into air at room temperature except for 2a and 2b. Electron spin resonance (ESR) spectra of the melt drawn fibers indicated that the plane of the square planar bis(ß‐diketonato)copper(II) complex in the fiber is oriented parallel to the fiber axis. X‐ray diffraction patterns from the melt‐drawn fibers are characterized by several sharp inner reflections at meridional position and a diffuse one at equatorial position, suggesting that the fibers possess an axial orientation with smectic A phase which is frozen in during melt‐drawn spinning.