| Abstract: | A novel spiro trialicyclic dianhydride, rel[1S,5R,6R]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐2′,5′‐dione) ( DAn ) was synthesized from itaconic anhydride ( 1 ) and cyclopentadiene via a Diels‐Alder reaction, nitric acid oxidation, and the subsequent dehydration with acetic anhydride. The structure of DAn was determined by NMR spectra and single crystal X‐ray diffraction. A series of soluble polyimides ( PI s) having a spiro alicyclic unit in the main chain were prepared by the reactions of DAn with several diamines through a general two‐step polymerization method. Polymerization temperature affected inherent viscosities of poly(amic acid)s. Chemically imidized PI s had the inherent viscosities in the range of 0.10–0.49 dL/g. Due to the unsymmetric spiro alicyclic structure, the PI s showed excellent solubility in many organic solvents. Glass transition temperatures of PI s ranged from 215 to 279°C and some of them showed no glass transition temperature. The 10% weight loss temperatures under nitrogen were in a range of 355–430°C. Films of PI s obtained by the thermal imidization were wholly transparent and colorless. |
