A simple method to fabricate polymer nanocomposites with single‐walled carbon nanotubes is reported, in which the nanotubes were reacted with poly(L ‐lysine) by using high‐speed vibration milling. The nanocomposites obtained were characterized by Fourier transform infrared (FT‐IR), UV–Vis spectroscopy, and thermogravimetric methods. The morphology as well as the dispersion of the carbon nanotubes were determined by scanning and transmission electron microscopy.
Nano-sized precipitated silica coated calcium carbonate fillers (PCC-Si) were modified by an alkyl- and a fluoro-alkoxysilane derivative, respectively. PCC-Si surface modification was characterized by elemental analysis, Fourier transform infrared analysis and X-ray photoelectron spectroscopy. The modification conditions used for surface treatment led to a similar grafting density (around 3.2 μmol m?2) for the two alkoxysilane derivatives. A significant decrease of filler hydrophilicity was observed after the alkoxysilane treatment. Nanocomposites prepared by melt mixing the modified fillers (10 wt.%) with polyvinylidene fluoride (PVDF) depicted no color change, an enhanced filler dispersion state with an homogeneous dispersion of very small filler aggregates (less than 150 nm diameter size), an increase of the thermal stability at high temperature and no change of the PVDF crystalline morphology. The oxygen permeability decrease measured on the nanocomposite prepared from the perfluorooctyltriethoxysilane modified filler was in good agreement with Maxwell law. The permeability increase evidenced for the nanocomposite based on the octyltriethoxysilane modified PCC suggested the formation of weak interfaces in this system. 相似文献
In this study, we report a two-step, one pot tandem microwave-assisted reaction of 3-formylchromones with aminopyrazoles followed by a tin-free radical addition. A library of alkyl substituted dihydropyrazolopyrimidines was prepared using this new process. 相似文献
In both his second and lost notebooks, Ramanujan introduced and studied a function \(k(q)=r(q)r^2(q^2)\), where \(r(q)\) is the Rogers–Ramanujan continued fraction. Ramanujan also recorded five beautiful relations between the Rogers–Ramanujan continued fraction \(r(q)\) and the five continued fractions \(r(-q)\), \(r(q^2)\), \(r(q^3)\), \(r(q^4)\), and \(r(q^5)\). Motivated by those relations, we present some modular relations between \(k(q)\) and \(k(-q)\), \(k(-q^2)\), \(k(q^3)\), and \(k(q^5)\) in this paper. 相似文献
In Nature, the family of copper monooxygenases comprised of peptidylglycine α‐hydroxylating monooxygenase (PHM), dopamine β‐monooxygenase (DβM), and tyramine β‐monooxygenase (TβM) is known to perform dioxygen‐dependent hydroxylation of aliphatic C? H bonds by using two uncoupled metal sites. In spite of many investigations, including biochemical, chemical, and computational, details of the C? H bond oxygenation mechanism remain elusive. Herein we report an investigation of the mechanism of hydroxylation by PHM by using hybrid quantum/classical potentials (i.e., QM/MM). Although previous investigations using hybrid QM/MM techniques were restricted to geometry optimizations, we have carried out ab initio molecular dynamics simulations in order to include the intrinsic flexibility of the active sites in the modeling protocol. The major finding of this study is an extremely fast rebound step after the initial hydrogen‐abstraction step promoted by the cupric–superoxide adduct. The hydrogen‐abstraction/rebound sequence leads to the formation of an alkyl hydroperoxide intermediate. Long‐range electron transfer from the remote copper site subsequently triggers its reduction to the hydroxylated substrate. We finally show two reactivity consequences inherent in the new mechanistic proposal, the investigation of which would provide a means to check its validity by experimental means. 相似文献
The Ramanujan Journal - We derive some new finite sums involving the sequence $$s_{2}\left( n\right) ,$$ the sum-of-digits of the expansion of n in base 2. These functions allow us to generalize... 相似文献