SYNTHESIS AND THE SMECTIC MESOPHASE OF COPOLYMERS CONTAINING A MESOGENIC (CARBAZOLYLMETHYLENE)ANILINE GROUP AS THE ELECTRON-DONOR AND A (4'-NITROBENZYLIDENE)ANILINE GROUP AS THE ELECTRON-ACCEPTOR

Side-chain liquid-crystalline copolymers containing a mesogenic (carbazolylmethylene)aniline group as an electron donor and a mesogenic (4-substituted benzylidene)aniline group with various electronegative groups were prepared. The copolymer prepared by copolymerization of 4-[[6-(methacryl-oyloxy)hexyl]oxy]-N-[(9-methylcarbazol-2-yl)methylene]aniline with 4-[[6-(methacryloyloxy)hexyl]oxy]-N-(4'-nitrobenzylidene)aniline exhibited smectic phases when the proportion of the mesogenic carbazolyl unit was in the range of 0.26-0.68, though the smectic phase did not appear in both homopolymers prepared from the individual monomers. The copolymer with the proportion of the carbazolyl group of 0.53 exhibited a wide smectic phase from 63 to 185-degrees-C. For the copolymer containing mesogenic carbazolyl and nitrophenyl groups, the X-ray reflection at 30.4 angstrom corresponded to the thickness of the smectic layer and the broad peak centered at 4.34 angstrom was assigned to the distance between the layers formed by the mesogenic side groups. The same tendency on thermal behaviors was observed for the copolymer containing mesogenic carbazolyl and cyanophenyl groups, while this tendency was not seen in the copolymer having carbazolyl and (4'-methoxybenzylidene)aniline units both of which were of electron-donating nature. For the copolymers containing both an electron-donating carbazolyl group and an electron-accepting nitrophenyl or cyanophenyl group, the appearance of the smectic phase and the enhancement in thermal stability might be caused mainly by interactions between pendant electron donor and acceptor mesogens.