Adhesion properties of 12FPMDA-based polyimides containing a trifluoromethylphenyl moiety

Abstract

3,6-Di(3′,5′-bis(trifluoromethyl)phenyl)pyromellitic dianhydride (12FPMDA) was synthesized in our laboratory and utilized to prepare polyimides with diamines such as bis(3-aminophenyl)-3,5-bis(trifluoromethyl)phenyl phosphine oxide (mDA6FPPO), bis(3-aminophenyl)-4-trifluoromethylphenyl phosphine oxide (mDA3FPPO) and bis(3-aminophenyl)phenyl phosphine oxide (mDAPPO). For comparison, 3,6-di(4′-trifluoromethylphenyl)pyromellitic dianhydride (6FPMDA), 3,6-diphenyl pyromellitic dianhydride (DPPMDA) and pyromellitic dianhydride (PMDA) were also utilized. Polyimides were synthesized via a two-step process: preparation of poly(amic acid) in p-chlorophenol with isoquinoline as catalyst, followed by solution imidization at the reflux temperature of p-chlorophenol for 12 h, with polymer molecular weight controlled to 20 000 g/mol by adding excess dianhydride. Polyimides were then characterized by FT-IR, NMR, GPC, DSC and TGA, and subjected to solubility, solution viscosity, water absorption and coefficient of thermal expansion (CTE) measurements. Adhesion properties were evaluated with a T-peel test with silane/Crcoated or bare Cu foils. Polyimides prepared with 12FPMDA exhibited well controlled molecular weight (18 000- 18 900 g/mol), reasonable intrinsic viscosity (0.27-0.29 dl/g), high glass transition temperature (Tg) (293-324 °C), good thermal stability (>500 °C in air), low water absorption (1.19-1.93 wt%), fairly low CTEs (39-49 ppm/ °C) and good adhesion properties (76.2-84.0 g/mm) with silane/Cr-coated Cu foils.

Keywords:

• POLYIMIDE
• FLUORINE
• PHOSPHINE OXIDE
• ADHESION
• CTE
• WATER ABSORPTION