Aromatic polyimides containing cyclopropylamide fragment as pendant group. A study of the balance between solubility and structural rigidity

Aromatic polyimides (PIs) containing a cyclopropylamide moiety as bulky polar pendant group were prepared in high yield and were structurally characterized. Polyimides containing 4,4’-hexafluoroisopropyliden diphthalic anhydride and bis(3,4-dicarboxyphenyl)dimethylsilane anhydride were soluble in aprotic polar organic solvents, while those PI derived from benzophenone-3,3′,4,4′-tetracarboxylic dianhydride with a keto central unit was insoluble. The relationship between bulky pendant group and the nature of the central moiety of the dianhydride monomer respect to the thermal properties of the PIs was studied. All PIs were thermally stable showing thermal decomposition temperature with the 10% weight loss (TDT10%) between 425-480 ºC. The glass transition temperature (Tg) values range between 265 and 315 °C. Mechanical properties from films of a selected PI were tested too.