The Experts below are selected from a list of 188844 Experts worldwide ranked by ideXlab platform
Krzysztof Matyjaszewski - One of the best experts on this subject based on the ideXlab platform.
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synthesis of molecular brushes by grafting onto Method combination of atrp and click reactions
Journal of the American Chemical Society, 2007Co-Authors: Krzysztof MatyjaszewskiAbstract:Molecular brushes (densely grafted polymers or bottle-brush macromolecules) were synthesized by the “grafting onto” Method via combination of atom transfer radical polymerization (ATRP) and “click” reactions. Linear poly(2-hydroxyethyl methacrylate) (PHEMA) polymers were synthesized first by ATRP. After esterification reactions between pentynoic acid and the hydroxyl side groups, polymeric backbones with alkynyl side groups on essentially every monomer unit (PHEMA-alkyne) were obtained. Five kinds of azido-terminated polymeric side chains (SCs) with different chemical compositions and molecular weights were used, including poly(ethylene glycol)-N3 (PEO-N3), polystyrene-N3, poly(n-butyl acrylate)-N3, and poly(n-butyl acrylate)-b-polystyrene-N3. All click coupling reactions between alkyne-containing polymeric backbones (PHEMA-alkyne) and azido-terminated polymeric SCs were completed within 3 h. The grafting density of the obtained molecular brushes was affected by several factors, including the molecular we...
Cheng Yang - One of the best experts on this subject based on the ideXlab platform.
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anion conductive poly 2 6 dimethyl 1 4 phenylene oxide grafted with tailored polystyrene chains for alkaline fuel cells
Journal of Membrane Science, 2019Co-Authors: Yingda Huang, Junping Dong, Cheng Yang, Nanwen LiAbstract:Abstract A series of polystyrene (PS)-grafted poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) having pendent quaternary ammonium groups were synthesized as anion exchange membranes (AEMs) by the “grafting onto” Method via a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed click chemistry. The length of PS grafting chains was controlled readily during ATRP. As expected, the polystyrene grafting chains showed excellent miscibility with PPO backbone. Therefore, transparent, flexible and tough membranes were obtained by solution casting. The miscible PS grafting chains induced well-defined hydrophobic-hydrophilic separation of the as-obtained PPO AEMs as confirmed by small-angle X-ray scattering (SAXS) technology. Moreover, the hydrophobic grafting chains can effectively control the water absorption, and thus improve the dimensional stability of AEMs in water. The PS-grafted AEMs showed higher IEC-normalized hydroxide conductivity but lower water uptake than the typical AEM without PS side chains, which may be attributed to the well-defined micro-phase separation in AEMs. The highest hydroxide conductivity of 15.9 mS/cm was achieved at 20 °C in spite of its low IEC value of 1.21 meq./g. Alkaline stability testing in 1 M NaOH at 80 °C demonstrated that PS-grafted PPO AEMs with side-chain-type QA cations showed excellent alkaline stability as evidenced by the change of hydroxide conductivity and the 1H NMR analysis after 500 h testing. Further H2/O2 alkaline fuel cell using PS-grafted PPO AEMs showed the maximum power density of 64.4 mW/cm2 at a current density of 140 mA/cm2, which is much higher than that of typical AEMs with C-16 alkyl grafting chains.
Nanwen Li - One of the best experts on this subject based on the ideXlab platform.
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anion conductive poly 2 6 dimethyl 1 4 phenylene oxide grafted with tailored polystyrene chains for alkaline fuel cells
Journal of Membrane Science, 2019Co-Authors: Yingda Huang, Junping Dong, Cheng Yang, Nanwen LiAbstract:Abstract A series of polystyrene (PS)-grafted poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) having pendent quaternary ammonium groups were synthesized as anion exchange membranes (AEMs) by the “grafting onto” Method via a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed click chemistry. The length of PS grafting chains was controlled readily during ATRP. As expected, the polystyrene grafting chains showed excellent miscibility with PPO backbone. Therefore, transparent, flexible and tough membranes were obtained by solution casting. The miscible PS grafting chains induced well-defined hydrophobic-hydrophilic separation of the as-obtained PPO AEMs as confirmed by small-angle X-ray scattering (SAXS) technology. Moreover, the hydrophobic grafting chains can effectively control the water absorption, and thus improve the dimensional stability of AEMs in water. The PS-grafted AEMs showed higher IEC-normalized hydroxide conductivity but lower water uptake than the typical AEM without PS side chains, which may be attributed to the well-defined micro-phase separation in AEMs. The highest hydroxide conductivity of 15.9 mS/cm was achieved at 20 °C in spite of its low IEC value of 1.21 meq./g. Alkaline stability testing in 1 M NaOH at 80 °C demonstrated that PS-grafted PPO AEMs with side-chain-type QA cations showed excellent alkaline stability as evidenced by the change of hydroxide conductivity and the 1H NMR analysis after 500 h testing. Further H2/O2 alkaline fuel cell using PS-grafted PPO AEMs showed the maximum power density of 64.4 mW/cm2 at a current density of 140 mA/cm2, which is much higher than that of typical AEMs with C-16 alkyl grafting chains.
Xiulin Zhu - One of the best experts on this subject based on the ideXlab platform.
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Design and Synthesis of a Cyclic Double-Grafted Polymer Using Active Ester Chemistry and Click Chemistry via A “Grafting onto” Method
MDPI AG, 2019Co-Authors: Meng Liu, Lu Yin, Shuangshuang Zhang, Zhengbiao Zhang, Wei Zhang, Xiulin ZhuAbstract:Combing active ester chemistry and click chemistry, a cyclic double-grafted polymer was successfully demonstrated via a “grafting onto„ Method. Using active ester chemistry as post-functionalized modification approach, cyclic backbone (c-P2) was synthesized by reacting propargyl amine with cyclic precursor (poly(pentafluorophenyl 4-vinylbenzoate), c-PPF4VB6.5k). Hydroxyl-containing polymer double-chain (l-PS-PhOH) was prepared by reacting azide-functionalized polystyrene (l-PSN3) with 3,5-bis(propynyloxy)phenyl methanol, and further modified by azide group to generate azide-containing polymer double-chain (l-PS-PhN3). The cyclic backbone (c-P2) was then coupled with azide-containing polymer double-chain (l-PS-PhN3) via CuAAC reaction to construct a novel cyclic double-grafted polymer (c-P2-g-Ph-PS). This research realized diversity and complexity of side chains on cyclic-grafted polymers, and this cyclic double-grafted polymer (c-P2-g-Ph-PS) still exhibited narrow molecular weight distribution (Mw/Mn < 1.10)
Meng Liu - One of the best experts on this subject based on the ideXlab platform.
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Design and Synthesis of a Cyclic Double-Grafted Polymer Using Active Ester Chemistry and Click Chemistry via A “Grafting onto” Method
MDPI AG, 2019Co-Authors: Meng Liu, Lu Yin, Shuangshuang Zhang, Zhengbiao Zhang, Wei Zhang, Xiulin ZhuAbstract:Combing active ester chemistry and click chemistry, a cyclic double-grafted polymer was successfully demonstrated via a “grafting onto„ Method. Using active ester chemistry as post-functionalized modification approach, cyclic backbone (c-P2) was synthesized by reacting propargyl amine with cyclic precursor (poly(pentafluorophenyl 4-vinylbenzoate), c-PPF4VB6.5k). Hydroxyl-containing polymer double-chain (l-PS-PhOH) was prepared by reacting azide-functionalized polystyrene (l-PSN3) with 3,5-bis(propynyloxy)phenyl methanol, and further modified by azide group to generate azide-containing polymer double-chain (l-PS-PhN3). The cyclic backbone (c-P2) was then coupled with azide-containing polymer double-chain (l-PS-PhN3) via CuAAC reaction to construct a novel cyclic double-grafted polymer (c-P2-g-Ph-PS). This research realized diversity and complexity of side chains on cyclic-grafted polymers, and this cyclic double-grafted polymer (c-P2-g-Ph-PS) still exhibited narrow molecular weight distribution (Mw/Mn < 1.10)
