Aromatic polyimides for optoelectronic applications

Aromatic polyimides have been prepared by solution polycondensation reaction of different aromatic diamines having preformed 1,3,4-oxadiazole ring with naphthalene-1,4,5,8-tetracarboxylic acid dianhydride (DNTA) or with a mixture of this dianhydride with hexafluoroisopropylidene-dianhydride (6FDA). The copolyimides containing naphthalene and flexible hexafluoroisopropylidene groups were soluble in polar amidic solvents and their solutions gave flexible thin films when spread onto glass plates and very thin films with smooth surface by spin coating. The thermal stability and glass transition temperature of these polyimides and copolyimides were measured and compared with regard to the influence of naphthalene units on these physical properties. The UV-vis and photoluminescence properties were also investigated.