Search results for "tyre"
showing 10 items of 586 documents
Directed Assembly of Soft Colloids through Rapid Solvent Exchange
2015
We studied the directed assembly of soft nanoparticles through rapid micromixing of polymers in solution with a nonsolvent. Both experiments and computer simulations were performed to elucidate the underlying physics and to investigate the role of various process parameters. In particular, we discovered that no external stabilizing agents or charged end groups are required to keep the colloids separated from each other when water is used as the nonsolvent. Furthermore, the size of the nanoparticles can be reliably tuned through the mixing rate and the ratio between polymer solution and nonsolvent. Our results demonstrate that this mechanism is highly promising for the mass fabrication of un…
A fluorescent molecular sensor for pH windows in traditional and polymeric biocompatible micelles: comicellization of anionic species to shift and re…
2011
A new approach is presented to obtain fluorescent sensors for pH windows that work in water and under biomimetic conditions. A single molecule that features all-covalently linked components is used, thus making it capable of working as a fluorescent sensor with an OFF/ON/OFF response to pH value. The components are a tertiary amine, a pyridine, and a fluorophore (pyrene). The forms with both protonated bases or both neutral bases quench the pyrene fluorescence, whereas the form with the neutral pyridine and protonated amine groups is fluorescent. The molecular sensor is also equipped with a long alkyl chain to make it highly hydrophobic in all its protonated and unprotonated forms, that is,…
[The in vitro effect of the addition of ion exchange resins on the bioavailability of electrolytes in artificial enteral feeding formulas].
2008
Objective: To determine in vitro free ion concentration in 3 standard artificial enteral feeding formulas following the addition of ion exchange resins. Method: Three standard types of AEF were chosen: Osmolite HN®, Nutrison Standard®, and Isosource Standard®. The ion exchange resins used were: sodium polystyrene sulfonate and calcium polystyrene sulfonate. In a beaker were mixed 100 mL of AEF with 1.5 g or 3 g of ion exchange resins for 48 hours at 37oC. Subsequently, the samples were precipitated and the supernatant obtained was used for determining the concentrations of calcium, magnesium, sodium, and potassium ions. Results: The addition of sodium polystyrene sulfonate to different type…
ChemInform Abstract: Covalently Supported Ionic Liquid Phases: An Advanced Class of Recyclable Catalytic Systems
2016
In this review, the most recent advances in the synthesis and catalytic applications of covalently supported ionic liquid (IL) phases will be discussed. This class of recyclable catalytic materials is based on the covalent attachment of several types of ammonium salts, usually imidazolium, but also thiazolium, triazolium, and pyrrolidinium salts, on the surface of different supports, for example, silica, periodic mesoporous organosilica, polystyrene, magnetic-based materials, carbon nanotubes (NTs), halloysite NTs, polyhedral oligomeric silsesquioxane (POSS), and fullerenes. Moreover, poly(ionic liquid) materials, in which the IL-based structure also acts as a support, will be considered. T…
Solution properties of polyelectrolytes. III. Effect of sodium polystyrene sulfonate concentration on viscometric and size exclusion chromatographic …
1988
The effect of sodium polystyrene sulfonate concentration on the shape of its molecules in aqueous solution at different NaNO3 ionic strengths has been analyzed by viscometry and size-exclusion chromatography (s.e.c). An equation has been developed which predicts the intrinsic viscosity, [η] p.cp.cs, at finite concentration of both polyion (cp) and electrolyte (cs). The experimental results obtained by both techniques can be accounted for in terms of the theory. Several factors involved in the elution mechanism have been considered and the variation of the slopes of s.e.c. calibration curves with cp and cs has been discussed in terms of polyion conformation changes.
Solution properties of polyelectrolytes. I. Exclusion chromatography of sodium polystyrene sulphonate in salt-free water as eluent
1987
The effect of concentration of sodium polystyrene sulphonate on the elution volume in exclusion chromatography has been investigated using salt-free water as eluent. A non-linear increase in the elution volume has been observed with increasing injected sample concentration. Concentration-dependent calibrations have been obtained which approach the universal calibration for uncharged polymers (dextrans) as polyelectrolyte concentration increases. The separation mechanisms are interpreted in terms of electrostatic and hydrodynamic interactions. A semi-empirical model is proposed to predict concentration effects of linear polyions in exclusion chromatography and good agreement has been found b…
Zur Gelpermeationschromatographie in organischen Lösungsmitteln
1965
Die Gelpermeationschromatographie hat sich vor allem mittels der Sephadexgele fur die Trennung polymerhomologer wasserloslicher Makromolekule als sehr erfolgreich erwiesen. Die Trennung nur in organischen Losungsmitteln loslicher Polymerer ist erst in jungster Zeit gelungen, wobei vernetzte Polystyrol-, Polymethacrylat- und Dextranderivatgele benutzt werden. Der Mechanismus dieses chromatographischen Prozesses wird untersucht. Ein Vergleich dieses Vorganges, bei dem das Polymere nur in einer Phase vorliegt, mit den klassischen Methoden, die mit Auftrennung in zwei Phasen arbeiten, wird durchgefuhrt. Insbesondere werden die Methoden der Dreiecks-Fallungsfraktionierung, der Kolonnentechnik mi…
Disproportionierung und Kombination als Abbruchsmechanismen bei der radikalischen Polymerisation von Styrol, 2. Analyse der temperaturabhängigkeiten
1975
Styrol wurde in Substanz mit 14C-markiertem 2,2′-Azoisobutyronitril im Temperatur-bereich von 30 bis 80°C polymerisiert. Aus der Polymerisationsgeschwindigkeit und der Anzahl der radioaktiven Endgruppen im Polymeren wurden die Effektivitat des Starters f und die Verhaltnisse der Geschwindigkeitskonstanten fur Wachstum, Abbruch und Start k/ka und ka, PR/(kwkst) berechnet. Die Bestimmung der Molekulargewichtsverteilungen mit Hilfe der Gelpermeationschromatographie ermoglichte es, die Ubertragungskonstante CM und das Verhaltnis ka, disp/ka, comb zu berechnen. Die Temperaturabhangigkeiten der Geschwindigkeitskonstanten erwiesen sich als physikalisch sinnvoll. Styrene was bulk polymerised by ini…
Disproportionierung und kombination als abbruchmechanismen bei der radikalischen polymerisation von styrol, 1.Versuche mit 14C-markierten 2,2′-azoiso…
1975
Die Substanzpolymerisation von Styrol mit 14C-markiertem 2,2′-Azoisobutyronitril (AIBN) wurde bei 52°C experimentell untersucht. Die Polymerisation wurde dilatometrisch verfolgt, die Molekulargewichte der entstandenen Polymeren viskosimetrisch ermit-telt, der Gewichtsbruch der einkettigen Molekule gelchromatographisch bestimmt und die Anzahl der markierten Endgruppen ausgezahlt. Die eingehende kinetische Analyse erhartet die neueren Erkenntnisse uber den Abbruchmechanismus. Danach liegt bei der Polymerisation von Styrol neben der Kombination auch Disproportionierung vor. Bulk polymerisation of styrene initiated by 14C-labelled 2,2′-azoisobutyronitrile (AIBN) was studied at 52°C. The polymer…
Transesterification of rapeseed oil over acid resins promoted by supercritical carbon dioxide
2011
The methanolysis of rapeseed oil catalyzed by commercial styrene-divinylbenzene macroporous acid resins was performed in a batch reactor at 100-140 °C and 10-46 MPa to study the effect of supercritical carbon dioxide (scCO2) on the performances of the process. Reaction temperatures of 120-140 °C were necessary to obtain high enough yields of fatty acid methyl esters. Upon addition of scCO2 faster transesterification kinetics was obtained also at the lowest investigated operating pressure (10-11 MPa), working in two fluid phase systems. Experiments performed changing the reaction time indicated that most of the esters were formed during the first 3 h. When the pressure was increased at 38-46…