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1.
Hellweg T. Schemmel S. Rother G. Brlet A. Eckerlebe H. Findenegg G.H. 《The European physical journal. E, Soft matter》2003,12(1):1-4
The European Physical Journal E - The temperature-induced microphase separation of the binary liquid system iso-butyric acid+heavy water (iBA + D2O) in a mesoporous silica glass (CPG-10-75) of... 相似文献
2.
Amphiphilic diblock copolymers consisting of a hydrophobic polystyrene block (PS) and a hydrophilic poly(ethylene oxide)
block (PEO) with block sizes of 1000 or 3000 g/mol for both blocks were studied at the air/water and toluene/water interface.
Measurements of the film pressure π of spread monolayers at the water surface reveal two limiting regimes of the π−a
m isotherms, in which the mean molecular area a
m is determined either by the size of the hydrophilic or the hydrophobic blocks of the PS-PEO molecules. The interfacial activity
of the block copolymers at the toluene/water interface was studied by measuring the interfacial tension σ over a wide range
of concentrations. Pronounced differences in the temperature dependence of the interfacial tension were observed, depending
mostly on the block length of the hydrophilic PEO block. From the temperature dependence of σ it is inferred that for the
block copolymers with the PEO block size of 3000 g/mol the phase inversion temperature (PIT) is well above 60 °C while for
those with a PEO block size of 1000 g/mol the PIT is below or near 25 °C in the toluene/water system.
Received: 5 February 1998 Accepted: 16 February 1998 相似文献
3.
Summary Ellipsometry has been applied to study the adsorption of sodium dodecylsulfate (NaDS) at the air/solution interface of the surfactant in water and aqueous sodium chloride. Results are expressed by the ellipticitye and the anglea which the major axis of the ellipse forms with the plane of incidence of the light. The ellipticity is found to change its sign at low NaDS concentrations and to pass a maximum somewhat below the cmc. Below the maximum the increment in ellipticity Aee is a linear function of the surface excess concentration dodecylsulfate. The slope e/gd this linear relation is found to decrease when inert electrolyte (NaCl) is added. The azimuth anglea increases slightly with NaDS concentration near and above the cmc. The results are discussed in terms of the Drude theory.
Zusammenfassung Die Adsorption von Natrium Dodecylsulfat (NaDS) an der Oberfläche wäßßriger Lösungen wurde mit Hilfe eines Ellipsometers untersucht. Die Meßergebnisse werden durch die Elliptizität e und den Winkel a zwischen der Hauptachse der Ellipse und der Einfallsebene des Lichtstrahls ausgedrü ckt. Die Elliptizität wechselt ihr Vorzeichen im Bereich geringer Konzentrationen von NaDS und läuft durch ein Maximum etwas unterhalb der cmc des Tensids. Unterhalb des Maximums wird eine lineare Beziehung zwischen dem Inkrement der Elliptizität e und der Oberflächen-Überschußkonzentration von Dodecylsulfat gefunden. Durch Zugabe eines inerten Elektrolyten (NaC1) wird die Steigung e/ stark verringert. Der Azimuth-Winkel a nimmt im Bereich der cmc des Tensids schwach zu. Die Ergebnisse werden im Rahmen der Drude-Theorie diskutiert.相似文献
4.
G. H. Findenegg K. Gruber J. F. Pereira Friedrich Kohler 《Monatshefte für Chemie / Chemical Monthly》1965,96(2):669-678
Zusammenfassung Es wird der Aufbau eines Kalorimeters zur Bestimmung der spezif. Wärme von Flüssigkeiten beschrieben. Die Messungen werden nach einem kontinuierlichen adiabatischen Aufheizverfahren durchgeführt. Der Fehler in der Molwärme beträgt ca. ±0,4%. Die Methode erlaubt auch innerhalb relativ kleiner Temperaturbereiche eine Aussage über die Temperaturabhängigkeit der Wärmekapazität.Die Molwärme des Systems 1,2-Dibromäthan-Benzol wird zwischen 24 und 29°C über den ganzen Konzentrationsbereich vermessen. Die Mischungen zeigen negative C
p-Werte mit unsymmetrischem Konzentrationsverlauf. Für höhere Temperaturen ist eine Zunahme der Symmetrie zu erwarten.
Mit 3 Abbildungen 相似文献
A calorimeter has been described which serves to determine the heat capacities of liquids. In the measurements the calorimeter and the surroundings are heated continuously, so that adiabatic conditions prevail. The experimental error in the molar heat capacities is ca. ±0,4%. The method also permits the estimation of the temperature dependence of the heat capacities, even within relatively small temperature intervals.The molar heat capacity of the system 1,2-dibromoethane-benzene has been measured between 24° and 29°C for all concentrations. The C p-values of the mixtures are negative and show an asymmetrical dependence on the concentration. For higher temperatures it is expected that the concentration dependence will become more nearly symmetrical.
Mit 3 Abbildungen 相似文献
5.
Summary The chromatographic technique of frontal analysis is applied to measuring adsorption from binary liquid mixtures by silica gel. The complete adsorption isotherm of a solvent mixture is obtained by measuring the break-through curves for a series of small concentration steps of the mobile phase. This method offers a direct way to determine the composition of the stationary phase in liquid-solid chromatography with mixed mobile phases. The surface excess isotherms of all binary systems formed by benzene, cyclohexane, and 1,2-dichloroethane, at the solution-silica gel interface at 25 °C are presented. The data of the three systems are shown to be thermodynamically mutually consistent. 相似文献
6.
Bharti B Meissner J Findenegg GH 《Langmuir : the ACS journal of surfaces and colloids》2011,27(16):9823-9833
The interaction of the globular protein lysozyme with silica nanoparticles of diameter 20 nm was studied in a pH range between the isoelectric points (IEPs) of silica and the protein (pH 3-11). The adsorption affinity and capacity of lysozyme on the silica particles is increasing progressively with pH, and the adsorbed protein induces bridging aggregation of the silica particles. Structural properties of the aggregates were studied as a function of pH at a fixed protein-to-silica concentration ratio which corresponds to a surface concentration of protein well below a complete monolayer in the complete-binding regime at pH > 6. Sedimentation studies indicate the presence of compact aggregates at pH 4-6 and a loose flocculated network at pH 7-9, followed by a sharp decrease of aggregate size near the IEP of lysozyme. The structure of the bridged silica aggregates was studied by cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering. The structure factor S(q) derived from the scattering profiles displays characteristic features of particles interacting by a short-range attractive potential and can be represented by the square-well Percus-Yevick potential model, with a potential depth not exceeding 3k(B)T. 相似文献
7.
Gerhard H. Findenegg Prof. Dr. Susanne Jähnert Dr. Dilek Akcakayiran Dr. Andreas Schreiber Dr. 《Chemphyschem》2008,9(18):2651-2659
In nanosized pores, liquid water can be thermodynamically stable down to temperatures well below the limit of homogeneous nucleation of bulk water (~235 K). Studies of water in such pores therefore offer an opportunity to reveal the anomalous behavior of deeply supercooled water. Herein we focus on recent studies of the limits of freezing and melting of water in the cylindrical pores of ordered mesoporous silicas with pore diameters in the range of 2–10 nm, based on vapor sorption measurements, calorimetric studies, NMR spectroscopy and cryoporometry, and neutron diffraction studies. 相似文献
8.
In this work, micro-column liquid chromatography has been employed for the study of the adsorption of ethylene glucol monoether (C8E4) and pentaethylene glucol monoether (C10E5) nonionic surfactants into the nanopores of SBA-15 silica at two temperatures. The adsorption process for both the surfactants has been investigated in the range of concentration from very dilute solution to "just above" critical micelle concentration (CMC). The adsorption data for both the surfactants are characterized as typical LC-shaped isotherms with plateau near the CMC. A simple two-step adsorption model has been applied to represent an experimental data. An attempt to estimate the thickness of the surfactant layer in the pores, from the experimental data, has been made. 相似文献
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10.
The effect of repeated cycles of water adsorption/desorption on the structural stability of ordered mesoporous silica SBA-15 is studied by small-angle x-ray scattering (SAXS). In?situ sorption measurements are conducted using a custom-built sorption apparatus in connection with a laboratory SAXS setup. Two striking irreversible changes are observed in the sorption isotherms as derived from the integrated SAXS intensity. First, the capillary condensation pressure shifts progressively to lower relative pressure values with increasing number of sorption cycles. This effect is attributed to chemisorption of water at the silica walls, resulting in a change of the fluid-wall interaction. Second, the sorption cycles do not close completely at vanishing vapour pressure, suggesting that progressively more water remains trapped within the porous material after each cycle. This effect is interpreted to be the result of an irreversible collapse of parts of mesopores, originating from pore wall deformation due to the large Laplace pressure of water acting on the pore walls at capillary condensation and capillary evaporation. 相似文献