In the first stage, a series of aromatic diamine compounds such as 2-methoxy-5,4'-diaminodiphenyl ether (ODAOMe) and 2-trifluomethyl4,4'-diaminodiphenyl ether (ODACF(3)) were synthesized. These aromatic diamines and 4,4'-diaminodiphenyl ether (ODA) were then used to prepare copolyimides with 4,4'-oxydiphthalic anhydride (ODPA) and bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA). Both chemical composition and the arrangements of repetitive units were characterized by H-1 and F-19 NMR. It was shown that solubility and thermal stability are related to the BCDA fraction in the copolymers and to the chemical structure of the diamine.