A new pyridazine-containing aromatic diamine monomer

3

6-bis(3-aminophenoxy)pyridazine

was successfully synthesized by a nucleophilic substitution reaction of 3

6-dichloropyridazine with meta-aminophenol in the presence of potassium hydroxide in dimethyl sulfoxide (DMSO).1H-NMR

FTIR and HPLC-MS were employed to confirm the diamine and intermediates structure.In order to maintain the thermal and mechanical properties

and improve the glass transition temperatures (Tg) and optical property

the novel aromatic heterocyclic diamine monomer was employed to synthesize a series of polyimides by polycondensation with various commercial aromatic dianhydrides in N

N-dimethylacetamide (DMAc) via the conventional two-step method

i.e.

ring-opening polycondensation forming the poly(amic acid)s (PAA) and further thermal imidization forming the pyridazine-containing polyimides.The resulting PAA possessed inherent viscosities in the range of 0.37~0.50 dL/g.High quality polyimide films could be prepared by casting the PAA solutions on glass plates.Experimental results indicated that the polyimide films had good thermal stability

with high initial decomposition temperature (Td 409 ℃) and Tg of 188~241 ℃

and the temperature at 5% and 10% weight loss of 421~448 and 458~473 ℃ at a nitrogen atmosphere

respectively.Moreover

the polyimide films showed outstanding mechanical properties with tensile strength of 46~102 MPa

tensile modulus of 2.7~3.5 GPa and elongation at break of 2.0%~6.5%.Most of the polyimide films had good chemical resistance

and were insoluble in common organic solvents

such as NMP

DMSO

DMF

m-cresol and CHCl3.The UV-Visible measurements indicated that the cut-off wavelength of polyimide films was in the range of 367~389 nm.The pyridazine-based polyimide films showed a good combination of properties.