THE ROLE OF THE PYRIMIDINE RING IN THE MAIN-CHAIN OF POLYAMIC ACIDS AND POLYIMDES .3. COMPARISON OF PROPERTIES OF POLYPYROMELLITAMIC ACIDS BASED ON 2,5-BIS(P-AMINOPHENYL)PYRIMIDINE AND 4,4''-DIAMINOTERPHENYL

A comparative study of the behavior of polypyromellitamic acids based on 2,5-bis(p-aminophenyl)pyrimidine and 4,4''-diaminoterphenyl in conc entrated dimethylacetamide solutions was carried out by the light-scat tering method. It was shown that mutual ordering of the scattering ele ments is much higher for the pyrimidine-containing polyamic acids than for benzenoid polyamic acids. The Flory-Huggins parameters of the pol ymer-solvent interaction thus determined indicate that the polymer-pol ymer interactions increase when a pyrimidine ring is introduced into t he polyamic acid or polyimide. Hence, the hypothesis postulating that the amide solvent is displaced by the pyrimidine ring during the shear packing of pyrimidine-containing polymers is confirmed.