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

This article describes the syntheses and second-order nonlinear optical (NL O) 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-diaminobe nzoate (DA1) and 5-(3-{4-[4-(N,N-dimethylamino)phenylazo]phenyl}sulfonylpro pyl)oxyisophthalic acid (IA1) or 5-(3-{N-methyl-4-[((4-methylsulfonylphenyl )azo]anilino}-1-propyl)oxyisophthalic acid (IA2). In the side chain of poly amide P3, which was obtained from DA1 and IA1, electron-donating and electr on-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 backbon e. The obtained polyamides exhibit relatively good solubility in common org anic solvents and provide optical-quality films upon spin-coating. The seco nd-harmonic generation (SHG) measurements of the obtained polyamides were c arried 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 a nd 16.5 pm/V, respectively.