Synthesis and Characterization of Polyimides from Unsymmetrical Diamine with Cyano Groups

A new diamine monomer containing cyano group, 2-cyano-4,4′-diaminodiphenyl ether, was synthesized and polymerized to polyimides with several aromatic dianhydrides via two kinds of imidization methods, namely, thermal or solution imidization methods. By the thermal imidization method, tough, flexible, and creasable polyimide films were obtained except the polyimide from pyromellitic dianhydride. The polyimides have high Tg values and are stable up to 500°C in air. The polyimide made from the diamine and 4,4′-oxyphthalic anhydride via solution imidization method was partially soluble in polar aprotic solvents, but it becomes soluble when the cyano groups are hydrolyzed.