Synthesis and Characterization of Soluble Polyimide with Short Side Chain

Three kinds of poly(amic acid)s were derived from aromatic diamines with short side chain (methyl or ethyl) as benzene side groups and 4,4′-oxydiphthalic anhydride (ODPA) via one-step polycondensation. Under the catalysis of triethylamine and dehydration of acetic anhydride, polyimides (PIs) were successfully synthesized from poly(amic acid)s through chemical imidization. FT-IR spectra of the PIs showed that the chemical imidization of poly(amic acid)s was complete. The solubility experiments proved that three kinds of PIs were soluble in common solvents, for example, polar aprotic solvents, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), even low boiling-point solvents, chloroform and tetrahydrofuran (THF). PI films were characterized by DSC, TG, spectrum analyzer, AC withstand voltage test device, resistance measuring instrument and electronic universal tensile machine. Results demonstrated that three kinds of PIs possessed excellent thermal stability, electrical insulation and good mechanical property.