Synthesis and characterization of novel semi-alicyclic polyimides from methyl-substituted tetralin dianhydride and aromatic diamines

The asymmetrical alicyclic dianhydride 3,4-dicarboxy-1,2,3,4-tetrahydro-6-methyl-1-naphthalene succinic dianhydride (MTDA, II) was synthesized from 4-methylstyrene and maleic anhydride under nitric oxide catalysis with a yield >70%. A series of semi-alicyclic polyimides (PIs) (PI–IIa∼PI–IId) were prepared by a one-step high temperature polycondensation procedure from MTDA and various aromatic diamines. For comparison, another series of PIs (PI–Ia∼PI–Id) were prepared from the analogous dianhydride 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride (TDA, I) and the same diamines. The asymmetrical molecular structure of MTDA endowed the derived PIs with good solubilities in common solvents and high optical transparencies in the ultraviolet and visible light regions by decreasing the intramolecular or intermolecular interactions of the polymer chains. The flexible and tough PI films exhibited good thermal stability up to 400 °C and showed glass transition temperatures in the range of 204–271 °C. The PI films exhibited good optical transparency with transmittances >80% at 400 nm, a cut-off wavelength <300 nm and a refractive index <1.54.