ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh-temperature mutual solubilities for some binary and ternary aqueous mixtures containing aromatic and chlorinated hydrocarbonsHerbert H. Hooper, Stefan Michel, and John M. PrausnitzCite this: J. Chem. Eng. Data 1988, 33, 4, 502–505Publication Date (Print):October 1, 1988Publication History Published online1 May 2002Published inissue 1 October 1988https://doi.org/10.1021/je00054a032RIGHTS & PERMISSIONSArticle Views151Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (378 KB) Get e-Alerts Get e-Alerts
Two commercially available amine-cured epoxy resin formulations were studied under different environmental conditions with regard to the surface tension evolution using axisymmetric drop shape analysis (ADSA). By employing a new strategy, ADSA was used to monitor simultaneously the surface tension and the density of these reactive mixtures from sessile drops. The kinetics of the bulk reactions were quantified by Fourier transform infrared (FTIR) spectroscopy, and the changes in the molecular composition of the surface region were studied by X-ray photoelectron spectroscopy (XPS). In both formulations, the surface tension values of the amine hardeners were lower than those of the epoxy resins. For one system, the surface tension of the mixture was similar to the surface tension of the hardener. In this case, the hardener migrates to the surface and determines the surface tension of the mixture, as could be proved by XPS measurements. In the other case, the surface region contained only a very small amount of nitrogen, indicating that the nitrogen-containing groups of the hardener were not enriched in the surface region of this mixture. Its surface tension was similar to that of the pure epoxy resin. In a controlled argon atmosphere, the surface tension of the reactive epoxy–amine systems considered here changed very little as the curing reaction proceeded. The time-dependent changes of the surface tension of the mixtures were caused by environmental factors, particularly the presence of carbon dioxide and water. Such factors can produce complicated surface tension responses due to surface reactions with the amine hardener. The extent of these changes can be controlled by the migration of the hardener to the surface region.
By employing a new strategy presented recently by Wulf etal., axisymmetric drop shape analysis (ADSA) can be used to determine simultaneously the surface tension and the density of polymer melts from sessile drops at elevated temperatures. This required the modification of the ADSA algorithm to replace the density by the mass of the drop as input parameter and the development of a closed high temperature chamber whose temperature can be precisely controlled. In addition, special sample holders for the formation of pendant and sessile drops at elevated temperatures were needed. Recently, their design has been improved, which is described in this paper. For a commercial epoxy resin (DER 664 UE), it is shown that measurements with sessile drops yield essentially the same surface tension values and temperature coefficients as with pendant drops. The densities determined with ADSA are comparable to independent PVT results.
Control of pore opening is a valuable contribution to ensure filtration and separation of particles and cells of different sizes. These can be, e.g. blood cells with their cell distribution width, which is typically measured in the Complete Blood Count. In the current work, we investigate hydrogel pores made of pNIPAAm with swelling and de-swelling capabilities. They react to variations in ethanol concentration. Additionally, we analyze the effect of microfluidic pressure on membrane pores. Furthermore, the influence of the gel volume for cross-shaped pores is shown. For this purpose, experimental and numerical investigations are performed. An analogy model for the swelling behavior based on the Temperature-Expansion-Model from our previous work and a neo-Hookean material description is applied to describe swelling and mechanical deformation of the pores. Simulation results show a negligible influence to the pore bending in the specified pressure range. In the experiments, only a slight change in the pore area is observed under pressure variation. Nonetheless, there is a very good agreement between numerical and experimental results. The current investigations show the potential for the mechanical description of hydrogel pores for their further geometric optimization.
Recent developments in the field of covalent organic frameworks (COFs) describe the issue of processability. The precise tunability of delamination of such structures to obtain few layered nanosheets by synthetic control has been ventured in this study. Covalent anchoring of a series of linear and branched alkoxy side chains to the backbone of layered covalent organic frameworks was used to achieve this. To support the hypothesis, powder X-ray diffraction studies accompanied by computational modeling revealed that the elongation of side chains increases the interlayer distances of the COFs. This led to a successful study of the solvent-assisted exfoliation by atomic force microscopy techniques to obtain nanosheets with heights less than 2 nm, representing stacks of 4–5 layers. Dispersions of the functionalized COF nanosheets are stable for several hours. Furthermore, the surface properties are drastically changed, rendering the materials hydrophobic, with contact angles reaching up to 142° and complete blockage of the pore space toward water vapor. As a proof of concept, the sheets are processable and could be integrated into separators for lithium-ion batteries.
