SYNTHESIS AND CHARACTERIZATION OF SOLUBLE POLYIMIDES CONTAINING CYCLOHEXYLIDENE MOIETY WITH VARIOUS ALKYL-SUBSTITUENTS

A series of novel aromatic diamines containing kinked cyclohexylidene moieties was synthesized by a HCl-catalyzed condensation reaction of e xcess aniline and corresponding alkyl-substituted cyclohexanone deriva tives at 120-140 degrees C for 24 hours. The structures of monomers we re identifield by H-1-NMR, C-13-NMR, and FT-IR. The yields of monomer preparation were above 70%. The polymers were synthesized from the obt ained diamines and various aromatic dianhydrides by one-step polymeriz ation in m-cresol at 200 degrees C for 6-8 hours. The inherent viscosi ties were in the range of 0.74-1.66 dL/g and the prepared polyimides s howed excellent thermal stabilities as well as good solubility. That i s, all polymers were readily soluble in common organic solvents such a s dimethylacetamide, dimethylformamide, tetrahydrofuran, chloroform, e tc. and the glass transition temperatures were in the range of 261-348 degrees C. The solubility and the glass transition temperature of the polymers increased as the bulkiness of the alkyl-substituents increas ed.