The synthesis and characterization of polyimide homopolymers based on 5(6)-amino-1-(4-aminophenyl)1,3,3-trimethylindane

The isomeric diamine monomer 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylin dane (DAPI) was successfully synthesized via the dimerization of a-methylst yrene followed by nitration and reduction. High molecular weight, soluble p olyimides were synthesized via ester-acid solution imidization techniques a nd had glass-transition temperature values ranging from 247 to 369 degrees C. The polymers were soluble in common organic solvents because of the asym metric and nonplanar nature of DAPI and displayed good short-term thermal s tability by thermogravimetric analysis, as shown by their 5% weight-loss va lues above 500 degrees C in air. The DAPI/(3,4-dicarboxyphenyl) hexafluorop ropane dianhydride (6FDA) polyimide also showed 2-h thermal stability at 40 0 degrees C under nitrogen, despite the partial aliphatic character. Refrac tive index values as low as 1.571 were observed for DAPI/GFDA, which allows an estimated dielectric constant of 2.47 to be derived. The permeation of O-2 and N-2 was conducted on thin dense films. The bulky, bent, and isomeri c nature of DAPI imparted film-for ming membranes that permitted high O-2 p ermeability. In combination with 3,3',4,4'-benzophenone tetracarboxylic dia nhydride (BTDA), DAPI had a good combination of O-2 permeability and O-2/N- 2 selectivity values of 2.8 Ba and 7.3, respectively. The polymerization me thod utilized to facilitate the cyclization of DAPI/BTDA to the polyimide a ffected the final thermal properties of the resulting polymer. The chemical imidization of DAPI/BTDA generated a polyimide with a glass-transition tem perature value of 311 degrees C and a 5% weight-loss value in air of 451 de grees C. However, thermal and eater-acid imidization routes yielded an incr ease in the thermal properties. The ester-acid solution imidization of DAPI /BTDA produced a polymer glass-transition temperature value of 333 degrees C and a 5% weight-loss value of 525 degrees C in air. (C) 2000 John Wiley & Sons, Inc.