Yue Jin TONG, Yan Xiang CHENG, Meng Xian DING, Yan XING, Yong Hua LIN
中国化学快报. 1998, 9(10): 971-972.
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X-ray crystal structures of 2,2',3,3'-and 3,3',4,4-biphenyltetracarboxylic dianhydride (2,2',3,3'-and 3,3',4,4'-BPDA) were determined. The dianhydride isomers have different symmetry caused by difference in two anhydride group positions and the dihedral angles between the two phenyl rings are 62.9°for 2,2',3,3',-BPDA and 0°for 3,3',4,4'-BPDA respectively. The polyimides from 2,2',3,3'-BPDA exhibit enhanced solubility, higher thermal stability, and higher glass transition temperature (Tg) compared with those from 3,3',4,4'-BPDA.