The influence of pentafluorophenyl groups on the nonlinear optical (NLO) performance of high generation dendrons and dendrimers
With the aim to make the influence of pentafluorophenyl groups in the periphery of high generation dendrons and dendrimers on their NLO performance clearly, some NLO dendrons and dendrimers with different chromophore moieties or different end-capped groups were carefully designed and investigated in detail. The results demonstrated that some strong Ar-ArF interactions between the pentafluorophenyl groups in the periphery and the normal phenyl rings of the donors, could influence the topological structures of dendrons or dendrimers, and then affect their NLO performance. Furthermore, the optical transparency and the stability of the dendrons and dendrimers with pentafluorophenyl groups as end-capped moieties were all improved, in comparison with normal dendrons and dendrimers containing phenyl ones as the end-capped groups.
Structure–function relationship exploration for enhanced electro-optic activity in isophorone-based organic NLO chromophores
Abstract Four isophorone-based chromophores FLD1-FLD4 has been synthesized and investigated based on julolidinyl donors, with modified isophorone-derived bridges and tricyanovinyldihydrofuran or phenyl-trifluoromethyl-tricyanofuran acceptors. The chromophore FLD3 was modified with a 2-((tert-butyldimethylsilyl)oxy)ethanethiol group covalently attached to the π-conjugate bridge to ensure its all-trans conformation and prevent close packing of molecules, which benefit the macroscopic electro-optic efficiency. The chromophore FLD3 possesses better thermal stability than chromophore FLD1 without the isolation group on the bridge. Moreover, density functional theory calculations suggested that the hyperpolarizability (β) value of chromophore FLD3 is larger than that of chromophore FLD1. Polymers doped with chromophore FLD3 have been poled to afford ultrahigh electro-optic coefficient (r33) of 238 pm/V at 1.31 μm, which is nearly 60% higher than that obtained from chromophore FLD1 and three times higher than that of analogue chromophores FLD2 and FLD4.
Dendronized tricyanopyrroline‐based chromophores in nonlinear optical active host polymer
We synthesized new nonlinear optical (NLO) chromophores containing a 3,5-bis(3,5-bisbenzyloxy-benzyloxy)-benzoate dendron. Tricyanopyrroline (TCP)-based chromophores were designed and prepared by virtue of its strong electron withdrawing property. A soluble polyimide containing 6-({4-[2-(1-allyl-4-cyano-5-dicyanomethylene-2-oxo-2,5-dihydro-1H-pyrrol-3-yl)-vinyl]-phenyll-butyl-amino)-hexanoyl group in the side chain was also prepared as an NLO active host polymer. A benzoate dendron was tethered at two different binding positions of the chromophore to yield two different guest molecules. Thin-film composites of these dendronized chromophores dissolved in the NLO active polyimide host were employed to fabricate the electro-optic (EO) samples. The EO properties of new NLO polyimides containing dendronized chromophores were compared with those of the sample with nondendronized plain chromophores. The effect of a bulky dendron on the EO properties was investigated using an in situ reflection technique.