Synthesis and characterization of new adamantane-based polyimides

A new adamantane-based dietheramine, 2,2-bis[4-(4-aminophenoxy)phenyl] adamantane, was prepared in two steps from chloro displacement of p-chloronitrobenzene with the potassium phenolate of 2,2-bis(4-hydroxyphenyl)adamantane, followed by hydrazine catalytic reduction of the intermediate dinitro compound. A series of polyimides with the adamantane-2,2-diyl unit as a cardo group was prepared from the adamantane-based dietheramine and various aromatic dianhydrides by a conventional two-stage synthesis in which the poly(amic acid)s obtained in the first stage were heated stage-by-stage at 150-270 degrees C to give the polyimides. The intermediate poly(amic acid)s had inherent viscosities between 0.82 and 1.66 dL/g. Except for the polyimide from pyromellitic dianhydride, all of the polyimides could be dissolved in NMP, and several polyimides also showed good solubility in other organic solvents. All of the polyimides were amorphous in nature as evidenced by X-ray diffractograms. The glass-transition temperatures (T-g) of these polyimides were recorded between 248 and 308 degrees C by differential scanning calorimetry (DSC), and the softening temperatures (T-s) determined by thermomechanical analysis (TMA) stayed in the range of 254-335 degrees C. Decomposition temperatures for 10% weight loss all occurred above 500 degrees C in both air and nitrogen atmospheres.