ORGANO-SOLUBLE POLYIMIDES - SYNTHESIS AND CHARACTERIZATION OF POLYIMIDES CONTAINING PHENYLATED P-BIPHENYL AND P-TERPHENYL UNITS

4,4'-diamino-2,2'-diphenylbiphenyl (1), 4,4''-diamino-2',3',5'-triphen yl-p-terphenyl (2a) and 4,4''-diamino-2',3',5',6'-tetraphenyl-p-terphe nyl (2b) have been polymerized with several aromatic dianhydrides in r efluxing m-cresol containing isoquinoline to afford a series of phenyl ated polyimides. The polymerization mixtures of 1 and 3,3',4,4'-biphen yltetracarboxylic dianhydride (BPDA) and 3,3'4,4'-benzophenonetetracar boxylic dianhydride (BTDA) and of 2a and pyromellitic dianhydride (PMD A) set to gel-like structures upon cooling. The gels, which displayed optical anisotropy typical of a liquid crystalline-like phase, could b e dissolved by heating and re-formed by cooling. Although the p-catena ted, rigid-rod polymers obtained from the diamines and PMDA were only soluble in concentrated sulphuric acid, the polymers that were prepare d from 1 and 2a and 3,3',4,4'-diphenylethertetracarboxylic dianhydride (ODPA), 3,3',4,4'-diphenylsulphonetetracarboxylic dianhydride (DSDA) and 2,2-bis[4(1 ,2-dicarboxyphenyl)]-1,1,1,3,3,3-hexafluoropropane dia nhydride (6FDA) were soluble in N-methyl-2-pyrrolidinone (NMP), m-cres ol and chlorinated solvents. In general, polymers prepared from 2a wer e the most soluble, while polymers prepared from 2b were the least sol uble. The intrinsic viscosities of the polymers ranged from 0.61 to 5. 1 dl g(-1) in concentrated sulphuric acid or NMP at 30 degrees C. The glass transition temperatures of most of the polymers could not be det ected with differential scanning calorimetry. The temperatures at whic h the polymers underwent 5% weight losses when subjected to thermal gr avimetric analysis ranged from 500 to 600 degrees C in both air and ni trogen. Several of the polymers could be solution cast into thin, wate r-white flexible films.