POLYMERIZATION, STRUCTURE AND THERMAL-PROPERTIES OF ODPA-DMB POLYIMIDE FILMS

A new high molecular weight polyimide based on 4,4'-oxidiphthalic anhy dride (ODPA) dianhydride and 2,2'-dimethyl-4,4'-diaminobiphenyl (DMB) diamine has been synthesized via a onestep polymerization method. This polyimide is soluble in phenolic solvents. Films from 7 to 30 mu m th ick were cast from the polymer solution and show in-plane orientation on a molecular scale detected by Fourier transform infrared spectrosco py experiments. This anisotropic structure leads to anisotropic optica l properties arising from two different refractive indices along the i n-plane and out-of-plane directions. ODPA-DMB possesses high thermal a nd thermo-oxidative stability. The glass transition temperature has be en determined to be 298 degrees C. Dynamic mechanical analyses show tw o relaxation processes appearing above room temperature: the beta- and the alpha-relaxation processes. The alpha-relaxation corresponds to t he glass transition while the beta-relaxation is a secondary relaxatio n process associated with the non-cooperative subsegmental motion.