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'-tetracarboxyl ic anhydride, or hexafluoroisopropylidene diphenyl-3,3',4,4'-tetracarb oxylic anhydride. These acetylated imide diphenols were polycondensed with substituted terephthalic acids or naphthalene-2, 6-dicarboxylic a cid. All poly(ester-imide)s, PEIs, derived from 3-aminophenol exclusiv ely formed isotropic melts. A thermotropic character was found for PEI s based on 4-aminophenol and diphenylether-3,3',4,4'-tetracarboxylic a cid. In contrast, the diphenylsulfone and isopropylidene diphenyl buil ding blocks proved to be unfavorable for the formation of liquid-cryst alline phases. Energy minima, bond angles, and torsion angles of the i mide units were calculated by a force-field program, and the experimen tal results are discussed on the basis of these theoretical data. Furt hermore, three different force-field programs are compared.