Synthesis of a new class of low-band-gap polymers with liquid crystalline substituents

New derivatives of poly(isothianaphthene methine) have been synthesized by a polycondensation reaction of 1,3-bis(tert-butyldimethylsilyl)isothianapht hene with benzaldehydes in the presence of POCl3. In the para position the benzaldehydes possesses a liquid crystalline group, which contains a phenyl cyclohexyl, phenylpyrimidine, or biphenyl moiety. The polymers are characte rized by IR, UV-vis-NIR, H-1 NMR, and C-13 NMR spectroscopy. All polymers a re soluble in common organic solvents and display band gaps between 1.2 and 1.3 eV and electrical conductivities in the, range of 10(-4)-10(-5) S/cM u pon iodine vapor doping.