SYNTHESIS OF CROSS-CONJUGATED(p-PHENYLENE)S-POLY(p-PHENYLENEVINYLENE)S HYBRIDS WITH LOW CONTENT OF STRUCTURAL DEFECTS

The novel shish-kebab-type liquid crystalline cross-conjugated (p-phenylene)s-poly(p-phenylenevinylene)s hybrid was synthesized through Gilch polymerization. Their structures and properties were characterized by NMR, GPC, DSC, X-ray diffraction and polarizing optical microscope (POM). ’H-NMR investigation of the polymers indicates that the shish-kebab-structure has a strong ability to suppress the structural defects in the polymers. The polymers are enantiotropic liquid crystals. The melting point (Tm) of the polymers decreases when the length of the alkoxy tails of the mesogenic units increases. The mesophase was identified by X-ray diffraction method. They showed not only a smectic LC phase, but also a strong green fluorescence in chloroform. The maximum absorption band of the "kebabs" of the two, 5-bis(4’-alkoxyphenyl)benzene at 280 nm did not appear in absorption spectra of the polymers. The same phenomena were also observed in the fluorescence spectra. These results imply that the polymers have formed a cross-conjugated uniform structure and achieved an extendedπ-conjugation polymer.