Adhesion property of novel polyimides with 1-[3?,5?-bis(trifluoromethyl)phenyl] pyromellitic dianhydride

Novel polyimides were synthesized from 1-[3',5'-bis(trifluoromethyl)phenyl] pyromellitic dianhydride (6FPPMDA) by a conventional two-step process: the preparation of poly(amic acid) followed by solution imidization via refluxing in p-chlorophenol. The diamines used for polyimide synthesis included bis(3-aminophenyl)-3,5-bis(trifluoromethyl)phenyl phosphine oxide, bis(3-aminophenyl)-4-trifluoromethylphenyl phosphine oxide, and bis(3-aminophenyl)phenyl phosphine oxide. The synthesized polyimides were designed to have a molecular weight of 20,000 g/mol by off-stoichiometry and were characterized by Fourier transform infrared, NMR, differential scanning calorimetry, and thermogravimetric analysis. In addition, their intrinsic viscosity, solubility, water absorption, and coefficient of thermal expansion (CTE) were also measured. The adhesion properties of the polyimides were evaluated via a T-peel test with bare and silane/Cr-coated Cu foils, and the failure surfaces were investigated with scanning electron microscopy. The 6FPPMDA-based polyimides exhibited high glass-transition temperatures (280-299 degrees C), good thermal stability (> 530 degrees C in air), low water absorption (1.46-2.16 wt %), and fairly low CTEs (32-40 ppm/degrees C), in addition to good adhesion properties (83-88 g/mm) with silane/Cr-coated Cu foils. (c) 2005 Wiley Periodicals, Inc.