Synthesis and Characterization of Copolyimides from s-BPDA/i-BPDA with Different Molar Ratio

A series of organosoluble copolyimides was successfully synthesized from the 2,2',3,3'-bipheny-ltetracarboxylic dianhydride(i-BPDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride(s-BPDA) with aro-matic diamine 4,4'-ODA.The copolyimides were characterized by FTIR,DSC,TGA and DMA.The copo-lyimides hold superior mechanical properties and show improved solubilities,depending on the i-BPDA con-tent.A regular increase of glass transition temperatures and a decrease of inherent viscosities of copolymers with increasing content of i-BPDA were also observed.