In this research, a series of porous copolyimide (co-PI) films containing trifluoromethyl group (CF3) were facilely prepared via a phase separation process. The co-PI were synthesized by the reaction of benzophenone-3,3,4,4-tetracarboxylic dianhydride (BTDA) with two diamines of 4,4-diaminodiphenyl ether (ODA) and 3-trifluoromethyl-4,4'-diaminodiphenyl ether (FODA) with various molar ratios. The flexible and tough porous co-PI films with about 300 m thickness and 8 approximate to 10 m average diameter could be obtained by solution casting conveniently. The thermal properties of the obtained porous co-PI films were excellent with a glass transition temperature at 270 degrees C approximate to 280 degrees C and only 5 weight loss in temperature from 530 degrees C to 560 degrees C under nitrogen atmosphere. In addition, the dielectric and hydrophobic properties of porous co-PI films were remarkably improved owing to the presence of trifluoromethyl groups (CF3) in the polymer chains. Moreover, our synthesized porous co-PI films also showed good mechanical properties. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44494.
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