Aromatic Polyazomethines Containing Phenylquinoxaline Rings

New aromatic polyazomethines have been synthesized by polycondensation of terephthalic dialdehyde with aromatic diamines containing preformed phenylquinoxaline rings. These polymers are easily soluble in polar aprotic solvents such as N-methylpyrrolidinone and dimethylacetamide, and even in less polar liquids like tetrahydrofurane and can be cast into thin flexible films or coatings from such solutions. They show high thermal stability with the initial decomposition temperature being above 500 °C and glass transition temperatures in the range 240–292 °C. The very thin polymer coatings deposited by a spin-coating technique onto silicon wafers show a very smooth, pinhole-free surface in atomic force microscopy investigations. The free-standing films of 20–30 μm thickness show a low dielectric constant, which is in the range 3.25–3.56, which is promising for a future application as high-performance dielectrics.