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Synthesis and characterization of spirobifluorene-based polyimides



The synthesis and properties of organosoluble aromatic polyimides, containing spiro-skeletal units in the polymer backbone on the basis of the spiro-diamine monomer, 2,2′-diamino-9,9′-spirobifluorene, are described. In the case of the spiro segment, the two fluorene rings are orthogonally arranged and connected through a tetrahedral bonding carbon atom, the spiro center. As a consequence, the polymer chain is periodically zigzagged with a 90° angle at each spiro center. This structural feature minimizes interchain interactions and restricts the close packing of the polymer chains, resulting in amorphous polyimides that have good solubility in organic solvents. Compared with their fluorene-based cardo analogues, the spirobifluorene-based polyimides have an improved solubility. Furthermore, the main-chain rigidity of the polyimide appears to be preserved because of the presence of the spiro structure, which restricts the free segmental mobility. As a result, these polyimides exhibit a high glass-transition temperature (Tg's) and good thermal stability. The Tg's of these polyimides were in the range of 287–374 °C, and the decomposition temperatures in nitrogen for a 10% weight loss occurred at temperatures above 570 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3615–3621, 2002