Synthesis and investigation of the properties of cardo‐copolyimides with different microstructure

Copolyimides, their microstructure being determined by the method of synthesis, were prepared by copolycondensation of 4,4′‐oxydiphthalic anhydride (1a), 4,4′‐carbonyldipthalic anhydride (1b), or 1,8:4,5‐naphthalenetetracarboxylic anhydride with a mixture of two diamines, hexa‐, octa‐, or dodecamethylene diamine (5a, 6a, 7a) and cardo‐diamines 9,9‐bis(4′‐aminophenyl)fluorene (3a) and 3,3‐bis(4′‐aminophenyl)phthalide (4) or two aromatic diamines, 4,4′‐oxydianiline (9) and 2,2‐bis(4‐aminophenyl)hexafluoropropane (8), at various mole ratios of the comonomers. Blockcopolyimides with five‐membered imide cycles were formed by catalytic imidization of the intermediate polymers prepared by addition of the solid dianhydride to a solution of the mixture of the two diamines, whereas the thermal cyclization of such polymers and the one‐step high‐temperature synthesis led to random copolyimides. The thermal and mechanical properties of the copolyimides with various microstructure and their solubility in organic solvents were compared.