A series of new polyimides was prepared by reacting 2,6-diaminopyridine with various aromatic dianhydrides in DMF in 1 : 1 mole ratio. All the resulting polyimides were readily soluble in organic solvents such as dimethylformamide, N,N-dimethylacetamide, pyridine, m-cresol, THF, etc. They also show good film-forming ability. The polyimides exhibit good thermal stability and mechanical properties. The polymers have high T g in the range of 252-296°C. The inherent viscosities of the polymers vary from 0.81 to 1.28 dL/g. A new class of bismaleimide and polyaspartimide as also synthesized. All the resulting polymer structures were characterized by FTIR and elemental analysis.
A series of organosoluble polyimides with various aromatic tetracarboxylic acid dianhydrides was prepared from diamine monomers using one-and two-step methods. All the polyimides were soluble in aprotic solvents such as NMP, DMF, DMAc, and DMSO. The polyimides showed excellent thermal stability and good mechanical properties. The glass-transition temperature of the prepared polyimides ranged from 2108C to 3258C. All the polyimides formed tough transparent films, with tensile strength of 84-118 MPa, 8%-12% elongation, and 1.5-2.3 GPa modulus. These polyimide films were found to have a dielectric constant in the range of 3.29-3.80 at 1 kHz and 3.14-3.76 at 10 kHz and low moisture uptake, 0.52%-1.10%.
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