POLYAMIDES FOR NONLINEAR OPTICS - SIDE-CHAIN ALL DONOR-ATTACHED NLO-PHORES VERSUS SIDE-CHAIN ALTERNATING DONOR-ATTACHED AND ACCEPTOR-ATTACHED NLO-PHORES

This article describes the syntheses and second-order nonlinear optica l (NLO) properties of a novel type of polyamide with side-chain altern ating donor-attached and acceptor attached NLO-phores as well as polya mide with side-chain all donor-attached NLO-phores. Two kinds of polya mides were prepared by condensation polymerization between 5-[2-(N-met hyl-4-nitroanilino)ethoxy]isophthaloyl chloride and 3-{[4-(dihexylamin o)phenyl]sulfonyl}propyl 3,5-diaminobenzoate (P3) or 2-[N-methyl-4-(oc tylsulfonyl)anilino]ethyl 3,5-diaminobenzoate (P4). In the side chain of P3, electron-donating and electron-withdrawing groups of the NLO-ph ores were alternatingly attached. The obtained polyamides exhibited go od solubility in common organic solvents and provided optical-quality films by spin-coating. The second-harmonic generation (SHG) measuremen ts of the obtained polyamides were carried out by the Maker fringe met hod using a Q-switched Nd:YAG laser as an exciting beam after corona-p oling at various temperatures, indicating that P3 and P4 exhibited the optimum second-order NLO coefficient, d(33), of 6.4 and 7.1 pm/V, res pectively. There were no significant differences in the temperature de pendence of orientational behavior between two kinds of polyamides. Th e preliminary measurements of the short-term temporal SHG decay sugges ted that it is possible for the relaxation of the NLO-phore orientatio n in P3 to be somewhat restricted, as far as deduced from the values o f time coefficient obtained by curve-fitting to the Si-IG decay curves .