Fully Conjugated and Soluble Polyazomethines

Abstract

Fully conjugated and soluble polyazomethines were synthesized by the polycondensation of aromatic dialdehydes with two kinds of diamines having a tetraphenylethylene structure, cis- and trans-1,2-bis(4-aminophenyl)-1,2-diphenylethylene (4a and 4b). The structures of these diamines were determined using NMR and single crystal X-ray analysis. The diamines formed 1:1 complexes with toluene which was used as a recrystallization solvent. The polyazomethines, as precipitated, possessed inherent viscosities (ηinh) in the range from 0.83 to 0.98 dL/g. Polymers 6 and 7, which were prepared from 4a and terephthalaldehyde and from 4b and isophthalaldehyde, respectively, gave flexible and tough orange films. These polymer films exhibited excellent solubility in common organic solvents such as benzene, chloroform, and THF. The molecular weights of the polymers increased 2- to 4-fold by postcuring at 200 °C. Although the crystallinity of polymer 6 was slightly higher than that of polymer 7, these polymers were essentially amorphous. All of the polyazomethines showed excellent thermal stability with no significant weight loss up to approximately 350 °C, and the 5% weight loss temperatures in air were over 400 °C. The polymer films had glass transition temperatures over 260 °C.