Abstract
Aromatic polyamides containing silicon and phenylquinoxaline rings in the main chain have been prepared by polycondensation reaction of a silicon-containing diacid chloride, namely bis( p-chlorocarbonylphenyl)-diphenylsilane, with various aromatic diamines having preformed phenylquinoxaline units. These polymers were easily soluble in polar aprotic solvents, such as N-methylpyrrolidinone (NMP) and dimethylformamide (DMF), and in tetrahydrofurane. They showed high thermal stability with decomposition temperature being above 450°C and glass transition temperature in the range of 253–304°C. Polymer solutions in NMP were processed into thin films having the thickness of tens of nanometer to 10 μm, by spin-coating onto glass plates or silicon wafers. The films had strong adhesion to substrates and exhibited very smooth surfaces, free of pinholes, in atomic force microscopy (AFM) studies. The free-standing films had dielectric constant in the range of 3.48–3.69. Thermal treatment of the films up to 350°C rendered them completely insoluble in organic solvents, while maintaining their smoothness and strong adhesion to the silicon substrate, and with no T g in DSC experiments. Their FTIR spectra did not show any changes compared to the untreated films, meaning that polymers maintain their structural integrity at high temperature.
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