Synthesis and properties of ultralow dielectric constant porous polyimide films containing trifluoromethyl groups

In this research, a series of porous copolyimide (co-PI) films containing trifluoromethyl group (CF 3 ) 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 μm thickness and 8∼10 μm 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 °C ∼ 280 °C and only 5% weight loss in temperature from 530 °C to 560 °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 (CF 3 ) in the polymer chains. Moreover, our synthesized porous co-PI films also showed good mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44494.