Search results for "Organic chemistry"
showing 10 items of 17180 documents
Sequestration of biogenic amines by alginic and fulvic acids.
2006
The interaction of natural (alginic and fulvic acids) and synthetic (polyacrylic acid 2.0 kDa) polyelectrolytes with some protonated polyamines [diamines: ethylendiamine, 1,4-diaminobutane (or putrescine), 1,5-diaminopentane (or cadaverine); triamines: N-(3-aminopropyl)-1,4diaminobutane (or spermidine), diethylenetriamine; tetramine: N.N'-bis(3-aminopropyl)-1,4-diaminobutane (or spermine); pentamine: tetraethylene-pentamine; hexamine: pentaethylenehexamine] was studied at T=25 degrees C by potentiometry and calorimetry. Measurements were performed without supporting electrolyte, in order to avoid interference, and results were reported at I=0 mol L(-1). For all the systems, the formation of…
Acid-Labile Surfactants Based on Poly(ethylene glycol), Carbon Dioxide and Propylene Oxide: Miniemulsion Polymerization and Degradation Studies
2017
Partially degradable, nonionic AB and ABA type di- and triblock copolymers based on poly(propylene carbonate) and poly(ethylene glycol) blocks were synthesized via immortal copolymerization of carbon dioxide and propylene oxide, using mPEG or PEG as a macroinitiator, and (R,R)-(salcy)-CoOBzF5 as a catalyst in a solvent-free one-pot procedure. The amphiphilic surfactants were prepared with molecular weights (Mn) between 2800 and 10,000 g·mol−1 with narrow molecular weight distributions (1.03–1.09). The copolymers were characterized using 1H-, 13C- and DOSY-NMR spectroscopy and size exclusion chromatography (SEC). Surface-active properties were determined by surface tension measurements (crit…
Halogen-Bonded Co-Crystals of Aromatic N-oxides : Polydentate Acceptors for Halogen and Hydrogen Bonds
2017
The C-ethyl-2-methylresorcinarene (1) forms 1:1 in-cavity complexes with aromatic N,N′-dioxides, only if each of the aromatic rings has an N−O group. The structurally different C-shaped 2,2′-bipyridine N,N′-dioxide (2,2′-BiPyNO) and the linear rod-shaped 4,4′-bipyridine N,N′-dioxide (4,4′-BiPyNO) both form 1:1 in-cavity complexes with the host resorcinarene in C4v crown and C2v conformations, respectively. In the solid state, the host–guest interactions between the 1,3-bis(4-pyridyl)propane N,N′-dioxide (BiPyPNO) and the host 1 stabilize the unfavorable anti-gauche conformation. Contrary to the N,N′-dioxide guests, the mono-N-oxide guest, 4-phenylpyridine N-oxide (4PhPyNO), does not form an…
Application of polydopamine functionalized zinc oxide for glucose biosensor design
2021
Zinc oxide (ZnO) nanostructures are widely used in optical sensors and biosensors. Functionalization of these nanostructures with polymers enables optical properties of ZnO to be tailored. Polydopamine (PDA) is a highly biocompatible polymer, which can be used as a versatile coating suitable for application in sensor and biosensor design. In this research, we have grown ZnO-based nanorods on the surface of ITO-modified glass-plated optically transparent electrodes (glass/ITO). Then the deposition of the PDA polymer layer on the surface of ZnO nanorods was performed from an aqueous PDA solution in such a way glass/ITO/ZnO-PDA structure was formed. The ZnO-PDA composite was characterized by S…
Comparative Investigation on the Soil Burial Degradation Behaviour of Polymer Films for Agriculture before and after Photo-Oxidation
2020
Polymer films based on biodegradable polymers, polyethylene (PE) and modified PE with oxo-degradable additive were prepared by film blowing. Carbon black (1%) was added to all the films. Commercial biodegradable Ecovio®
Naturally Occurring Oxazole Structural Units as Ligands of Vanadium Catalysts for Ethylene-Norbornene (Co)polymerization
2021
1,3-Oxazole and 4,5-dihydro-1,3-oxazole are common structural motifs in naturally occurring peptides. A series of vanadium complexes were synthesized using VCl3(THF)3 and methyl substituted (4,5-dihydro-1,3-oxazol-2-yl)-1,3-oxazoles as ligands and analyzed using NMR and MS methods. The complexes were found to be active catalysts both in ethylene polymerization and ethylene-norbornene copolymerization. The position of methyl substituent in the ligand has considerable impact on the performance of (co)polymerization reaction, as well as on the microstructure, and thus physical properties of the obtained copolymers.
On the effectiveness of different additives and concentrations on the re-building of the molecular structure of degraded polyethylene
2006
Mechanical recycling is an easy and economic way to re-use plastic waste as secondary materials, but, in general, their properties are worse with respect to the reclaimed materials and the virgin polymer. The aim of this work was to study the effect of concentration and reaction kinetics of two additives, an ethylene-co-glycidyl methacrylate (Lotader) and a hydroxylamine derivative (CGX), in the re-building of a degraded polyethylene. CGX is a nitroxyl radical generator able to form branching in polyolefins while the epoxy groups of Lotader can react with the functional groups present in the recycled polyethylene. The results indicate that the CGX has a higher reaction rate than Lotader, pr…
Transition metal complexes of tetradentate and bidentate Schiff bases as catalysts for ethylene polymerization: Effect of transition metal and cocata…
2009
This article compares catalytic performance of ethylene polymerization in similar polymerization conditions of transition metal complexes having two ligands [O,N] (phenoxy-imine) and having one tetradentate ligand [O,N,N,O] (salphen or salen). It is shown that the activity of both complex types as well as the product properties depend in the same way on the type of central metal in the complex and on the cocatalyst used. Although the type of ligand has some effect on the catalyst activity, yet it does not control the properties of the obtained products. The vanadium and zirconium complexes, irrespective of the cocatalyst used, yield linear polyethylene with high molecular weight (a few hund…
Weathering of low-density polyethylene grafted with itaconic acid in laboratory tests
2011
Polyethylene grafted with itaconic acid was subjected to weathering under laboratory accelerated conditions. The course of the photo-oxidative degradation process of that material was studied by FTIR spectroscopy both through quantitative measurements of changes in absorbance values at selected wave numbers and through measurements of surface area values for absorption bands which were separated by means of deconvolution. The use of both those procedures of quantitative determinations resulted in a general conclusion that the oxidation process was initiated from the very first moment of irradiation, and it produced ketones, acids, esters (intramolecular and of acetate type), peracids, peres…
Rheological Properties of Different Film Blowing Polyethylene Samples Under Shear and Elongational Flow
2005
Summary: The rheological behavior of polyethylenes ismainly dominated by the molecular weight, the molecularweight distribution and by the type, the amount and thedistribution of the chain branches. In this work a linearmetallocenecatalyzedpolyethylene(m-PE),abranchedme-tallocene catalyzed polyethylene (m-bPE), a conventionallinear low density polyethylene (LLDPE) and a low densitypolyethylene (LDPE) have been investigated in order tocompare their rheological behavior in shear and in elonga-tional flow. The four samples have similar melt flow indexand in particular a value typical of film blowing grade.The melt viscosity has been studied both in shear and inisothermal and non-isothermal elonga…