Novel polyamides for second-order nonlinear optics with side-chain azo-NLO-phores

Abstract

This article describes the syntheses and second-order nonlinear optical (NLO) properties of a novel type of polyamides with side-chain azo-NLO-phores. Two kinds of polyamides were prepared by condensation polymerization using 3-{N-methyl-4-[(4-methylsulfonylphenyl)azo]anilino]-1-propyl 3,5-diaminobenzoate (DA1) and 5-(3-{4-[4-(N,N-dimethylamino)phenylazo]phenyl}sulfonylpropyl)oxyisophthalic acid (IA1) or 5-(3-{N-methyl-4-[(4-methylsulfonylphenyl)azo]anilino}-1-propyl)oxyisophthalic acid (IA2). In the side chain of polyamide P3, which was obtained from DA1 and IA1, electron-donating and electron-withdrawing groups of the NLO-phores were alternatingly attached. In the side chain of polyamide P4, which was obtained from DA1 and IA2, electron-donating groups of all side-chain NLO-phores were attached to their backbone. The obtained polyamides exhibit relatively good solubility in common organic solvents and provide optical-quality films upon spin-coating. The second-harmonic generation (SHG) measurements of the obtained polyamides were carried out by the Maker fringe method using a Q-switched Nd: YAG laser as an exciting beam after corona-poling at various temperatures, indicating that P3 and P4 exhibit an optimum second-order NLO coefficient, d 33 , of 8.7 and 16.5 pm/V, respectively.