Novel polyimides derived from 2,3,3′,4′-benzophenonetetracarboxylic dianhydride

A series of polyimides (PIs) based on 2,3,3′,4′-benzophenonetetracarboxylic dianhydride (2,3,3′,4′-BTDA) and 3,3′,4,4′-BTDA were prepared by the conventional two-step process. The properties of the 2,3,3′,4′-BTDA based polyimides were compared with those of polyimides prepared from 3,3′,4,4′-BTDA. It was found that PIs from 2,3,3′,4′-BTDA have higher glass transition temperature and better solubility without sacrificing their thermal properties. Furthermore the rheological properties of PMR-15 type polyimide resins based on 2,3,3′,4′-BTDA showed lower melt viscosity and wider melt flow region (flow window) compared with those from 3,3′,4,4′-BTDA. The structure–property relations resulted from isomerism were discussed.