Synthesis and properties of polyimides containing 2,2′‐bipyridine derivatives

A series of polyimides containing 2,2′‐bipyridine, 7 , were synthesized by reaction of 4,4′‐diamino‐2,2′‐bipyridine ( 4 ) with various aromatic dianhydrides, followed by imidization upon heating. These polyimides are fairly thermostable, and 5% weight loss occurs in the range of 484°C‐580°C. The glass transition temperatures are between 276°C and 313°C. Their poly(amic acids) 6 can be partially quaternized using 1,2‐dibromoethane and then easily imidized upon heating. The temperature of quaternized polyimides at which 5% weight loss is observed is around 300°C, the glass transition temperatures range from 202–239°C. These quaternized polyimides can also develop color under UV irradiation in a poly( N ‐vinyl‐2‐pyrrolidone) (PVP) matrix with maximum absorption at 800 nm. The bipyridine‐based poly(amic acids) 6 can trap various metal ions from solution and then can be imidized by heating. The XPS data indicate the formation of a 1:1 (bipyridine: metal molar ratio) complex and a 2:1 complex. The temperature at which for the polyimide‐metal complexes 5% weight loss is observed is around 300°C. Both the poly(amic acid)‐metal complex and the polyimide‐metal complex catalyze the condensation of benzaldehyde with acetophenone, with yields of chalcone of ca. 6.7–31.7%. The order of catalytic activity for different metal ions is Zn(II) > Co(II) > Cu(II).