Home About us Contact
|
Home About us Contact | ||
|
|
||
Hyperbranched Polymers (Hyperbranch + polymer)
Selected AbstractsA New Carbazole-Constructed Hyperbranched Polymer: Convenient One-Pot Synthesis, Hole-Transporting Ability, and Field-Effect Transistor PropertiesADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Zhong'an Li Abstract A new hyperbranched polymer (HB-car), constructed fully by carbazole moieties, is successfully synthesized through a one-pot Suzuki coupling reaction. The resultant polymer is well-characterized, and its hole-transporting ability is studied carefully. The device, in which HB-car is utilized as a hole-transporting layer and tris-(8-hydroxyquinoline) aluminum as an electron-emitting layer as well as electron-transporting layer, gives a much higher efficiency (3.05,cd A,1), than that of a poly(N -vinylcarbazole) based device (2.19,cd A,1) under similar experimental conditions. The remarkable performance is attributed to its low energy barrier and enhanced hole-drifting ability in the HB-car based device. In addition, for the first time, a field-effect transistor (FET) based on the hyperbranched polymer is fabricated, and the organic FET device shows that HB-car is a typical p -type FET material with a saturation mobility of 1,×,10,5,cm2 V,1 s,1, a threshold voltage of ,47.1,V, and an on-to-off current ratio of 103. [source] Immobilisation of the BINAP Ligand on Dendrimers and Hyperbranched Polymers: Dependence of the Catalytic Properties on the Linker UnitADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Jutta Abstract A series of immobilised Carbo-BINAP ligands has been synthesised using poly(propylene imine) (PPI) dendrimers as soluble supports. They contain up to 64 BINAP ligands at their periphery without an additional linking unit. Despite the high steric requirements of the ligand, all dendrimers could be completely functionalised, resulting in the immobilised systems in good yields. Furthermore, the immobilisation strategy that worked out for the fixation of AMINAP ligands with additional linking units as well as of Carbo-BINAP ligands without additional linking units on dendrimers has thus been extended to less regularly hyperbranched poly(ethylene imines) (PEI) as soluble supports. In that way it has been possible to attach on average 9, 26, and 138 Glutaroyl-AMINAP or Carbo-BINAP ligands to PEIs of different molecular weights. The catalytic properties of these systems in the copper-catalysed hydrosilylation of acetophenone were investigated. The dendritic PPI-bound Carbo-BINAP ligands displayed a strong dependence of enantioselectivity and activity on the generation of the dendrimer. For the Carbo-BINAP and Glutaroyl-AMINAP ligands immobilised on the hyperbranched polymers, however, activities and enantioselectivities comparable to those of the mononuclear catalysts were found. The macromolecular, immobilised BINAP ligands could be recycled several times without any observable loss of activity or enantioselectivity. [source] Synthesis of Fluorinated Hyperbranched Polymers and Their Use as Additives in Cationic PhotopolymerizationMACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2005Marco Sangermano Abstract Summary: A fluorine containing hyperbranched polymer was synthesized by modifying an aromatic-aliphatic hyperbranched polyester with a semifluorinated alcohol via a Mitsunobu reaction and was subsequently used as an additive in cationic photopolymerization of an epoxy resin. The remaining OH groups of the fluorinated hyperbranched polymer interact with the polymeric carbocation through a chain-transfer mechanism inducing an increase in the final epoxy conversion. The fluorinated HBP induces modification of bulk and surface properties, with an increase in Tg and surface hydrophobicity already reached at very low concentration. The HBFP additive can, therefore, protect the coatings from aggressive solvents, increases hardness, and allows the preparation of a low energy surface coating. Synthesis of fluorinated hyperbranched polyester. [source] Models of Irregular Hyperbranched Polymers: Topological Disorder and Mechanical ResponseMACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2006Thorsten Koslowski Abstract Summary: We study the impact of topological disorder on the mechanical response of hyperbranched macromolecules from a theoretical and numerical perspective. The polymer models are generated using a bond switching algorithm, and the emerging systems are described within the Zimm and Rouse pictures of macromolecular dynamics. The topological disorder is manifest in the frequency-dependent dynamic moduli, . These are clearly distinct from that of regular hyperbranched fractals of the same size, and they do not obey simple scaling rules. The dynamic moduli reflect the short-range order inherent in the model, and we thus suggest that the extent of disorder in branched tree-like polymers may be well-estimated experimentally using . Model of an irregular hyperbranched polymer. [source] Synthesis and Characterization of the Nitrogen-Rich Hyperbranched Polymers , Poly([1,2,3]-Triazole-[1,3,5]-Triazine)sPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2008Georgiy Abstract Novel hyperbranched poly([1,2,3]-triazole-[1,3,5]-triazine)s (HBP TT) were synthesized by a 1,3-dipolar cycloaddition reaction from AB2 monomer , 2-azido-4,6-bis-prop-2-yn-1-yloxy- [1,3,5]-triazine (ABPOT). The monomer contains one azide group A and two terminal alkyne units B. Thermal polymerization of ABPOT in bulk or in DMF solution leads to hyperbranched polymers containing both 1,4- and 1,5-disubstituted [1,2,3]-triazoles. The monomer was also polymerized catalytically in the presence of Cu(I) salts under mild reaction conditions in DMSO solution and in bulk affording hyperbranched poly-[1,2,3]-triazoles 1,4-disubstituted only. The reactions lead to the products soluble in aprotic polar solvents like DMSO or DMF. Side reactions can proceed in a few cases, particularly: (i) homocoupling of alkyne groups, leading to the formation of insoluble products as a result of cross-linking, (ii) isomerization of propynyloxytriazine fragments to propynyl- or propadienyltriazinone ones, and (iii) hydrolysis of triple bonds without the loss of solubility. Heats of formation of monomer and synthesized polymers were calculated from their combustion heats. All products were characterized by NMR-, IR-spectroscopy, and size exclusion chromatography (SEC) data. The obtained results open the prospect for the use of HBP TT as the high-enthalpy modifiers for energetic and non-energetic binders. [source] Layer-by-Layer Deposition of Rhenium-Containing Hyperbranched Polymers and Fabrication of Photovoltaic CellsCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2007Chui Wan Tse Abstract Multilayer thin films were prepared by the layer-by-layer (LBL) deposition method using a rhenium-containing hyperbranched polymer and poly[2-(3-thienyl)ethoxy-4-butylsulfonate] (PTEBS). The radii of gyration of the hyperbranched polymer in solutions with different salt concentrations were measured by laser light scattering. A significant decrease in molecular size was observed when sodium trifluoromethanesulfonate was used as the electrolyte. The conditions of preparing the multilayer thin films by LBL deposition were studied. The growth of the multilayer films was monitored by absorption spectroscopy and spectroscopic ellipsometry, and the surface morphologies of the resulting films were studied by atomic force microscopy. When the pH of a PTEBS solution was kept at 6 and in the presence of salt, polymer films with maximum thickness were obtained. The multilayer films were also fabricated into photovoltaic cells and their photocurrent responses were measured upon irradiation with simulated air mass (AM) 1.5 solar light. The open-circuit voltage, short-circuit current, fill factor, and power conversion efficiency of the devices were 1.2 V, 27.1 ,,A,cm,2, 0.19, and 6.1×10,3,%, respectively. The high open-circuit voltage was attributed to the difference in the HOMO level of the PTEBS donor and the LUMO level of the hyperbranched polymer acceptor. A plot of incident photon-to-electron conversion efficiency versus wavelength also suggests that the PTEBS/hyperbranched polymer junction is involved in the photosensitization process, in which a maximum was observed at approximately 420 nm. The relatively high capacitance, determined from the measured photocurrent rise and decay profiles, can be attributed to the presence of large counter anions in the polymer film. [source] | |||||||||||||