Abstract
New thermotropic liquid crystalline polyimides (ηinh : 0.58-1.20 dLg-1) having aliphatic methylene chains and imide ring were prepared for the first time by the polycondensation under high pressure of the salt monomers derived from aliphatic diamines (number of methylene unit X=7-12) and diethyl 4, 4"-terphenyltetracarboxylate. Mesophases of the eight and eleven-membered polyimides were enantiotropic, whereas those of all the other polyimides were monotropic as observed by the DSC thermograms. According to the DSC and X-ray measurements, distinct odd-even effects were observed in which the mesophase properties and structures were significantly affected by the number of cabon atom in the flexible spacer. The smectic CA phase could be confirmed for the odd-membered polyimides from their wide angle X-ray diffraction patterns which exhibited an inner sharp reflection, so-called layer reflection, and an outer broad split reflection. On the other hand, the nematic phase could be confirmed for the even-membered polyimides. The transition temperature from crystal to liquid crystal transition or isotropic temperature upon heating and all transition temperatures upon cooling exhibited an odd-even effect with the number of methylene unit.
