For the first time, the indole-based NLO chromophores were embedded into the polymer main chain, and different isolation groups were attached to their donor side with the efforts of adjusting the NLO properties of the resultant main-chain polyurethanes, according to the site isolation principle. Thanks to the main-chain structure and the advantages of the indole-based chromophores, all the polymers show excellent transparency, good processability, thermal stability, and relatively good NLO effects. The tested NLO properties of the polymers demonstrate that there is a suitable isolation group present for the sulfonyl-based chromophore to boost its microscopic â value to a possibly higher macroscopic NLO property efficiently.

For the first time, a series of dendronlike main-chain polyurethanes have been successfully designed and synthesized, in which different isolation groups with different sizes were introduced to modify the subtle structure of the used "H"-type chromophores, according the concept of "suitable isolation groups". Thanks to the advantages of "H"-type chromophores and the introduced suitable isolation group, all of the polymers demonstrated large NLO effects, good processability, improved optical transparency, and thermal stability. The obtained experimental results indicated that the utilization of "H"-type chromophores might be a promising choice to efficiently translate the large-values of the organic chromophores into high macroscopic NLO activities of polymers.

Two new dendronized nonlinear optical (NLO) polyfluorenes were synthesized with high azochromophore loading density by the introduction of high generation chromophore dendrons on the side chains. Thanks to the advantages of Sharpless' click chemistry reaction, the dendrons were conveniently bonded to the backbone of polyfluorene with the conversion of 100%, although they were really very bulky. The new-formed triazole rings in the dendrons acted as suitable isolation groups to minimize the strong dipole-dipole interactions among the polar chromophore moieties to improveNLO effects, according to the results obtained from UV-vis spectra and order parameters. All the polymers were well characterized and exhibited good solubility, high thermal ability, wide optical window, and largeNLOeffects (up to 106.0 pm/V). In addition, the testedNLOresults of these dendronzied polymers demonstrated a deviation from the dipolar frustration that typically limits the NLO effect in conventional chromophore/polymer composite materials, indicating that the frequently observed asymptotic dependence of electro-optic activity on chromophore density may be overcome through rational design.

Department of Chemistry, Hubei Key Lab on Organic and Polymeric Opto-Electronic Materials, Wuhan UniVersity, Wuhan 430072, China, Organic Solids Laboratories, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, China, and Department of Chemistry, The Hong Kong UniVersity of Science & Technology, Clear Water Bay, Kowloon, Hong Kong

To develop sensitive and selective CN-chemosensors, a new imidazole-functionalized polyfluorene (P1) was designed and obtained conveniently, the fluorescence of which could be completely quenched by Cu2+ ions at the concentration as low as 0.20 ppm in diluted solutions. By utilizing the much higher stability constant of the complex of CN-and Cu2+, the quenched fluorescence of the solution of P1 by Cu2+ ions could recover upon the addition of trace CN-anions, with the detection limit down to 0.31 ppm, making P1 a novel, sensitive and selective cyanide probe.