POLYAMIDES FOR NONLINEAR OPTICS CONTAINING 2ND-ORDER NLO-PHORES WITH HIGH-DENSITY

This article describes the syntheses and second-order nonlinear optica l (NLO) properties of novel types of optically transparent polyamides containing second-order NLO-active chromophores with high density. The chromophore used in this study contained a perfluorooctylsulfonyl or cyano moiety as an electron-withdrawing group at the st-conjugating si tes. The polyamides were prepared by condensation polymerization betwe en 5-substituted isophthaloyl chloride derivatives and novel 3,5-diami nobenzoates. When the terminal groups in the side chain of each comono mer unit were different, amorphous polyamides exhibited good solubilit y in common organic solvents and provided optical-quality films by spi n-coating. The optical transparency of the obtained polyamides was dow n to 400 nm. Second-harmonic generation (SHG) measurements of the obta ined polyamides were carried out by the Maker fringe method using a Q- switched Nd:YAG laser as an exciting beam after corona-poling. One of the polyamides, which was prepared from 5-{ (4-cyanophenyl)-N-methylam ino]-ethoxy}isophthaloyl chloride and l-N-[4-(perfluorooctylsulfonyl)p henyl]amino}-ethyl 3,5-diaminobenzoate, exhibited the desired optical- transparency and the second-order NLO coefficient, d(33), of 4.4 +/- 1 .3 pm/V, retaining 94% of its original d(33) after storage for 2 weeks at ambient temperature.