Structure, phase (aggregate) state, and optical properties of a new heat-resistant polymer with a nonlinear optical chromophore

A new heat-resistant copolymer (II) with a nonlinear optical chromophore in a side chain was synthesized by the etherification of side hydroxyl groups in chains of silicon-containing poly(o-hydroxyamide) (I) with 4′-{(6-chlorohexyl)methylamino}-4-nitroazobenzene (chromophore) under conditions of phase-transfer catalysis. The structure and phase (aggregate) states of copolymer II were investigated using x-ray diffraction and differential scanning calorimetry. It was shown that the substitution of chromophore molecules for up to 15% of hydrogen atoms in hydroxyl groups of amorphous copolymer I most likely leads to an independent arrangement of the chromophoric groups and the formation of crystal domains. It was established that this ordering substantially affects the stability and efficiency of the nonlinear optical properties of films prepared from copolymer II and is probably responsible for the slow decay of the second-harmonic generation signal in the sample.