Synthesis and characterization of main-chain, second-order, nonlinear optical polyurethanes with isolation moieties and zigzag structures

摘要

In this study, two main-chain second-order nonlinear optical (NLO) polyurethanes were successfully prepared with indole-based chromophores. The introduced phenyl isolation group and the continuous zigzag polymer backbone were found to be helpful for effectively decreasing the intermolecular dipole-dipole interactions and enhancing the NLO properties of the resulting polymers. The studied polymers exhibited good optical transparency, high thermal stability, and excellent NLO effects; this indicated that the nonlinearity-stability trade-off and nonlinearity-transparency trade-off could be alleviated by this newly designed polymer system. Poly[4-anilinocarbonyl[N-ethoxy1-5-phenyl-3-azo(2'-oxyethylene-4'-nitrobenzene)indole]carbonylimino) with a zigzag backbone showed a large second harmonic generation coefficient (d(33)) value of 88.4 pm/V. However, poly[5-naphthyliminocarbonyl]N-ethoxyl-5-phenyl-3-azo(2'-oxyethylene-4`-nitrobenzene)indole]carbonylimino] (PUAZN) with a continuous zigzag structure exhibited a higher d(33) value of 116.2 pm/V, which was attributed to the unique rigid and zigzag linkage of 1,5-naphthalene as the isolation spacer. The enhanced NLO efficiency and relatively longer term temporal stability made PUAZN as a promising candidate for practical applications in photonic devices. (C) 2015 Wiley Periodicals, Inc.