Synthesis and photophysical properties of soluble polyimides and polyquinazolones containing side-chain chalcones or azo chromophores

Soluble aromatic and carboxyl- and hydroxyl-containing polyimides, mixed polyimides, and polyquinazolones of various chemical structures, as well as a series of new dicyanoazobenzene chromophores, are synthesized. From 20 to 80 mol % of chromophore groups are incorporated into side chains of the polymers. The thermal, photosensitive, and nonlinear optical properties (second-harmonic generation) of the chromophore-containing polymers are investigated. The polymers with covalently attached groups of the dye DR-13 or azo-derivatives of 4-phthalonitrile demonstrate the highest nonlinearity. The T _g values of the polyimides vary from 165 to 215°C; their temperatures corresponding to 5% weight loss lie in the range 290–350°C; and the measured coefficients of second-harmonic generation, d ₃₃, for a number of polarized films based on chromophore-containing polymers attain several tens of picometers per volt. The incorporation of chromophore groups into the side chains of the polymers causes an increase in the photosensitivity of polyimides by an order of magnitude relative to that of the parent polymers (S _0.1 = (3?4) × 10⁵ cm²/J in the range of dye absorption).