Aromatic diamine 4 containing 2

5-disubstituted pyrimidine structure was synthesized via a condensation reaction of vinamidium salts and amidine chloride salts

followed by hydrazine palladium catalyzed reduction.A series of homo- and co-polyimides containing pyrimidine units were prepared from the diamine and 1

4-phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3

3′

4

4′-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidizaton method.All of the polyimides showed excellent thermal stability and mechanical properties.The glass transition temperatures of the resulting polymides are in the range of 280～437℃

and the 5% weight loss temperatures are in the range of 545～588℃ in air.The polyimides films possess strength at break in the range of 185～282 MPa

elongations at break in the range of 9.1%～51% and tensile modulus in the range of 3.5～6.46 GPa.The polymer films are insoluble in common organic solvents exhibiting high chemical resistance.