Syntheses and characterizations of cardo polyimides based on new spirobifluorene diamine monomer

We synthesized a new spirobifluorene diamine monomer, 2,7-diamino-9,9-spirobifluorene (2,7-DASBF), in which two fluorene units are perpendicularly linked by the ‘spiro’ sp3 carbon, and two diamine groups are attached on the same fluorene ring. Two cardo polyimides were prepared from the polymerization of 2,7-DASBF with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (PI-1) or pyromellitic dianhydride (PI-2). The chemical structures of monomer and polymers were characterized by various spectroscopic techniques. Thermal stability, coefficients of thermal expansion and crystallinity of the resulting polyimides were investigated.