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Alkylammonium Cations (alkylammonium + cation)
Selected AbstractsMicrowave-Assisted Synthesis and Characterization of Poly(, -caprolactone)/Montmorillonite NanocompositesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2007Liqiong Liao Abstract Poly(, -caprolactone) (PCL)/montmorillonite (MMT) nanocomposites were prepared by in situ ring-opening polymerization of , -caprolactone in the presence of MMT modified by hydroxyl-group containing alkylammonium cation (Cloisite®30B) in a single mode microwave oven. For the polymerization mixtures, plateaus or exothermal peaks were observed in their temperature-time profiles and can be attributed to the heat-generating nature of the ring-opening polymerization. The morphologies of the nanocomposites showed a predominantly exfoliated structure. The mechanical properties of the nanocomposites were evaluated via dynamic mechanical analysis. Compared with that of the recovered PCL matrix, the mechanical properties of the PCL/Cloisite®30B nanocomposites showed obvious improvement. [source] Reduced Surfactant Uptake in Three Dimensional Assemblies of VOx Nanotubes Improves Reversible Li+ Intercalation and Charge CapacityADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Colm O'Dwyer Abstract The relationship between the nanoscale structure of vanadium pentoxide nanotubes and their ability to accommodate Li+ during intercalation/deintercalation is explored. The nanotubes are synthesized using two different precursors through a surfactant-assisted templating method, resulting in standalone VOx (vanadium oxide) nanotubes and also "nano-urchin". Under highly reducing conditions, where the interlaminar uptake of primary alkylamines is maximized, standalone nanotubes exhibit near-perfect scrolled layers and long-range structural order even at the molecular level. Under less reducing conditions, the degree of amine uptake is reduced due to a lower density of V4+ sites and less V2O5 is functionalized with adsorbed alkylammonium cations. This is typical of the nano-urchin structure. High-resolution TEM studies revealed the unique observation of nanometer-scale nanocrystals of pristine unreacted V2O5 throughout the length of the nanotubes in the nano-urchin. Electrochemical intercalation studies revealed that the very well ordered xerogel-based nanotubes exhibit similar specific capacities (235,mA h g,1) to Na+ -exchange nanorolls of VOx (200,mA h g,1). By comparison, the theoretical maximum value is reported to be 240,mA h g,1. The VOTPP-based nanotubes of the nano-urchin 3D assemblies, however, exhibit useful charge capacities exceeding 437,mA h g,1, which is a considerable advance for VOx based nanomaterials and one of the highest known capacities for Li+ intercalated laminar vanadates. [source] Morphology and properties of SAN-clay nanocomposites prepared principally by water-assisted extrusionPOLYMER ENGINEERING & SCIENCE, Issue 1 2010Michaël Mainil An efficient extrusion process involving the injection of water while processing was used to prepare poly (styrene- co -acrylonitrile) (SAN)/clay nanocomposites with a high degree of nanoclay delamination. The usefulness of water-assisted extrusion is highlighted here, in comparison with classical extrusion and roll mill processes. Cloisite® 30B (C30B), a montmorillonite clay organomodified with alkylammonium cations bearing 2-hydroxyethyl chains, and pristine montmorillonite were melt blended with SAN (25 wt% AN) in a semi-industrial scale extruder specially designed to allow water injection. XRD analysis, visual and TEM observations were used to evaluate the quality of clay dispersion. The relationship between the nanocomposite morphology and its mechanical and thermal properties was then investigated. The superiority of the SAN/C30B nanocomposite extruded with water has been evidenced by cone calorimetry tests and thermogravimetric measurements (TGA). These analyses showed a substantial improvement of the fire behavior and the thermal properties, while a 20% increase of the Young modulus was recorded. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Biodegradable polyester layered silicate nanocomposites based on poly(,-caprolactone)POLYMER ENGINEERING & SCIENCE, Issue 9 2002Nadège Pantoustier Nanocomposites based on biodegradable poly(,-caprolactone) (PCL) and layered silicates (montmorillonite, MMT) were prepared either by melt interaction with PCL or by in situ ring-opening polymerization of ,-caprolactone as promoted by the so-called coordination-insertion mechanism. Both non-modified clays (Na+ -MMT) and silicates modified by various alkylammonium cations were studied. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. Even at a filler content as low as 3 wt% of inorganic layered silicate, the PCL-layered silicate nanocomposites exhibited improved mechanical properties (higher Young's modulus) and increased thermal stability as well as enhanced flame retardant characteristics as a result of a charring effect. It was shown that the formation of PCL-based nanocomposites depended not only on the nature of the ammonium cation and related functionality but also on the selected synthetic route, melt intercalation vs. in situ intercalative polymerization. Interestingly enough, when the intercalative polymerization of ,-caprolactone was carried out in the presence of MMT organo-modified with ammonium cations bearing hydroxyl functions, nanocomposites with much improved mechanical properties were recovered. Those hybrid polyester layered silicate nanocomposites were characterized by a covalent bonding between the polyester chains and the clay organo-surface as a result of the polymerization mechanism, which was actually initiated from the surface hydroxyl functions adequately activated by selected tin (II) or tin (IV) catalysts. [source] | ||||||||||