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Hu R.,Hong Kong University of Science and Technology | Hu R.,HKUST Fok Ying Tung Research Institute Nansha | Lam J.W.Y.,Hong Kong University of Science and Technology | Lam J.W.Y.,HKUST Fok Ying Tung Research Institute Nansha | And 8 more authors.
Polymer Chemistry | Year: 2013

A facile approach for the synthesis of hyperbranched polyacrylates is developed. Tetraphenylethene-containing di- and tetra-acrylates are synthesized by esterification of bis(4-hydroxylphenyl)diphenylethene and tetrakis(4-hydroxylphenyl)ethene with acryloyl chloride and polymerized using azobisisobutyronitrile in refluxing THF, furnishing high molecular weight (Mw up to 87100) polyacrylates with glycogen-like structures and closed-loops in nearly quantitative yields (isolation yield up to 99%). All the polymers are soluble in common organic solvents and are thermally stable with degradation temperatures up to 357 °C under nitrogen. Whereas the monomers and polymers are nonemissive or faintly emissive in solutions, they become strong emitters in the aggregated state, demonstrating a phenomenon of aggregation-induced or enhanced emission. The emission of the monomer and polymer spots on the TLC plates can be turned "off" and "on" continuously and reversibly by wetting and dewetting processes by vapors of organic solvents. The polymers are photosensitive and UV irradiation of their films through copper masks crosslinks the exposed parts, generating fluorescent negative photoresist patterns. The polymers possess good optical transparency and show high refractive indices (RI = 1.6825-1.5653) in a wide wavelength region (400-1700 nm) with low chromatic dispersion. The emission of the polymer nanoaggregates can be quenched efficiently by picric acid with large quenching constants up to 2.07 × 105 M-1, suggesting that they are sensitive fluorescent sensors for explosive detection. The fluorescent polymers become weakly emissive when hydrolyzed under appropriate conditions, implicative of their utility in controlled drug delivery. © 2013 The Royal Society of Chemistry. Source


Jim C.K.W.,Hong Kong University of Science and Technology | Jim C.K.W.,HKUST Fok Ying Tung Research Institute Nansha | Qin A.,Hong Kong University of Science and Technology | Qin A.,HKUST Fok Ying Tung Research Institute Nansha | And 10 more authors.
Advanced Functional Materials | Year: 2010

A new synthetic route to sulfur-rich polymers has been developed. The alkyne polyhydrothiolations of 4,4'-thiodibenzenethiol (1) and arylene dipropiolates (2-5) mediated by amines proceed at room temperature in a regioselective fashion, furnishing sole anti-Markovnikov products of poly(vinylenesulfide)s (P1/2-P1/5) with high molecular weights (Mw up to 32 300) and high stereoregularities (Z content up to 81.4%) in high yields (up to 98.2%). Polymers P1/2-P1/4 are soluble in common organic solvents. They are optically transparent, allowing almost all visible and IR light to transmit through. Thanks to the high sulfur contents of the polymers, their films show high refractive indices (n = 1.73-1.70) in the wavelength region of 5001700 nm as well as high Abbé numbers (vD' up to 539) and low optical dispersions (D' down to 0.002) at wavelengths important for telecommunications. Their refractivities can be further enhanced (n up to 2.06) by metal complexation and their films can be crosslinked by UV irradiation, which enables ready fabrication of fluorescent photopatterns. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA. Source

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