ABSTRACT:Soluble copolyimides based on 2,3,5-tricarboxycyclopentyl acetic dianhydride (TCA-AH)/aromatic tetracarboxilic dianhydrides/diamino diphenyl ether (DDE) were obtained. The maximum incorporation ratios of aromatic dianhydrides depend on flexibility of the dianhydrides. The ratios increase in the order of pyromellitic dianhydride (PMDA) (25 mo!%), 3,3' ,4,4' -biphenyltetracarboxylic dianhydride (BPDA) ( 50 mo!%) and 3,3' ,4,4' -benzophenonetetracarboxylic dianhydride (BTDA) (65 mo!%). The incorporation of conventional aromatic tetracarboxilic dianhydrides results in improvement of the thermal stability of soluble polyimides based on TCA-AH by the increment of aromatic components in polymer backbone, and the reduction of amount of a special monomer, that is TCA-AH.KEY WORDS Polyimide / Soluble Polyimide / Copolymerization / 2,3,5-Tricarboxycyclopentyl Acetic Dianhydride / Soluble Copolyimide / Thermal Stability / Polyimides exhibit excellent thermal and mechanical properties, and have extensive engineering and microelectronics applications. 1 Aromatic polyimides such as pyromellitic polyimides are prepared from aromatic diamines and aromatic tetracarboxylic dianhydrides via poly(amic acid)s. Since conventional aromatic polyimides are insoluble, these polymers are usually processed as the corresponding soluble poly(amic acid) precursors, and then either thermally or chemically imidized. However, there are some problems owing to the unstability of poly(amic acid)s and the liberation of water in imidization process. Therefore, solvent soluble polyimides processed without difficulty are desired. The solubility of the polyimides has been successfully improved by the incorporation of fluorine moieties 2 -6 or, chlorine moieties 7 or, bulky side groups 8 or, pendant phenyl groups 9 or, polydimethylsiloxane segment, 10 or polyalicyclic structures 11 -13 into the polymer backbone. Because these modifications are generally carried out using relatively expensive special monomers, soluble polyimide copolymers which consist of common aromatic dianhydrides and diamines have been also investigated. 14 Recently the authors reported the synthesis and characterization of soluble polyimides prepared from an alicyclic tetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentyl acetic dianhydride (TCA-AH), and aromatic diamines. 15 TCA-AH polyimides exhibited good thermal stability and 10% weight loss temperatures were in the range of 422--470°C in air and 457--494°C in nitrogen. These temperatures are about 100°C lower than the values of aromatic soluble polyimides based on fluorin containing monomers such as 4,4' -hexafluoroisopropylidenedi(phthalic anhydride) (6FDA). This paper reports the synthesis and characterization of soluble copolyimides based on TCA-AH and conven-222 tional aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA). The object of this study is to reduce the amounts ofTCA-AH ...