Isomeric dianhydrides based modified phenylethynyl-terminated addition-type imide oligomers

Two series of addition-type imide oligomers derived from asymmetric 2,3,3',4'-biphenyltetra-carboxylic dianhydride (a-BPDA) and isomeric 2,3,2',3-biphenyltetracarboxylic dianhydride (i-BPDA) or 3,3',4,4'-oxydiphthalic dianhydride (ODPA) with 4,4'-oxydianiline (4,4'-ODA) and 4-phenylethynyl-phthalic anhydride (PEPA) were prepared and characterized. All imide co-oligomers having molecular weight of 2500 g mol(-1) (n=4) showed good solubility in NMP, which has 40% (w/v) solid content. The thermal curing process of the oligomers was investigated by Fourier transform-infrared and differential scanning calorimetry (DSC). The rheological behaviors showed that the oligomers have low melt viscosity above 300 degrees C. The glass transition temperature of the cured imide oligomer films was measured by DSC and dynamic mechanical analysis, and found to be related to the structure of polymer chain. The tensile and thermal properties of the cured films were evaluated. Solubility, thermal and tensile properties of oligomers with different molecular weights were also investigated.