Liquid-Crystalline Polyimides. 12. Fully Aromatic Thermotropic Poly(Ester-imide)s Derived from Diphenylether-3,3′,4,4′-Tetracarboxylic Imide

Acetylated imide diphenols were prepared from 3- or 4-aminophenol and diphenylether-3,3′,4,4′-tetracarboxylic anhydride, benzophenone-3,3′,4,4′-tetracarboxylic anhydride, diphenylsulfone-3,3′,4′,4′-tetracarboxylic anhydride, or hexafluoroisopropylidene diphenyl-3,3′,4,4′-tetracarboxylic anhydride. These acetylated imide diphenols were polycondensed with substituted terephthalic acids or naphthalene-2, 6-dicarboxylic acid. All poly(ester-imide)s, PEIs, derived from 3-aminophenol exclusively formed isotropic melts. A thermotropic character was found for PEIs based on 4-aminophenol and diphenylether-3,3′,4,4′-tetracarboxylic acid. In contrast, the diphenylsulfone and isopropylidene diphenyl building blocks proved to be unfavorable for the formation of liquid-crystalline phases. Energy minima, bond angles, and torsion angles of the imide units were calculated by a force-field program, and the experimental results are discussed on the basis of these theoretical data. Furthermore, three different force-field programs are compared.