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Formation of porous polymer morphology by microsyneresis during divinylbenzene polymerization 下载免费PDF全文
Libuše Hanková Ladislav Holub Karel Jeřábek 《Journal of Polymer Science.Polymer Physics》2015,53(11):774-781
This article describes the investigation of the importance of various reaction conditions on microsyneretic pore formation during polymerization of divinylbenzene (DVB) under so‐called “solvothermal” conditions. To induce microsyneretic pore formation, the most important parameter is an unusually high dilution of monomers with a “good” porogen solvating the polymer chains. High dilution and solvation of the growing poly(DVB) chains promote the prolongation of the polymer chains rather than their interconnection by crosslinking. Consequently, when the polymer gel density reaches the point where syneresis starts, the polymer network is geometrically too extensive to be broken up into precipitating entities and, instead, porogen droplets are formed within the continuous polymer gel. The pore geometry created by microsyneresis offers high surface area in wide mesopores and hence, high capacity for supporting functional groups or reactions with much better accessibility than narrow pores between polymer microspheres produced by macrosyneresis in conventional styrenic polymer supports. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 774–781 相似文献
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W. Libuś B. Janaszewski R. Pastewski H. Twardowska 《Journal of solution chemistry》1980,9(10):737-752
Solubility isotherms are reported for the NiCl2·4py, MnCl2·4py, and MnCl2·2py solid pyridinates in a number of pyridine+diluent mixtures at 25°C. Activity coefficients of the solvent components have been derived from the total vapor pressures measured by a static method. The standard free energies of transfer for the NiCl2py4 and MnCl2py4 complexes are the same, within the experimental error, in the pyridine+aprotic diluent mixtures, while marked differences are observed in the pyridine+chloroform mixtures. Marked deviations are observed for chloroform and 1,2-dichloroethane from a correlation between the standard free energy of transfer of the complexes, on one hand, and the Hildebrand's solubility parameter of the solvent, on the other, the latter correlation being roughly valid for aprotic solvents. The deviations are tentatively ascribed to hydrogen bond formation of the type H... between the protic solvents and the coordinated pyridine molecules, enhanced by the d electron delocalization. 相似文献
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Libuše Kišová 《Monatshefte für Chemie / Chemical Monthly》1970,101(2):484-492
Zusammenfassung Die Wechselstrompolarographie ist für die Messung der Geschwindigkeitskonstanten der Elektrodenprozesse im Bereich von 5·10–3–5·10–2 cm sec–1 anwendbar. Das bestätigen auch die Ergebnisse, die für ein Modellsystem erhalten wurden. Experimentell wurde die Anwendbarkeit der Methode am Redoxsystem [CrCl2(H2O)4]+–[CrCl2(H2O)4] in sauren 4–9n-LiCl-Lösungen nachgeprüft, und zwar durch den Vergleich der Resultate mit den Ergebnissen der Messungen derFaraday-impedanz und der Methode der überlagerten Spannung.
Mit 7 Abbildungen 相似文献
Application of alternating current polarography for the measurement of rate constants
The method of alternating current polarography is known to be applicable to the measurement of rate constants of electrode reactions within the range of 5·10–3 to 5·10–2 cm sec–1. This follows also from the results obtained with model systems. The applicability of the method has been studied in the redox-system [CrCl2(H2O)4]+–[CrCl2(H2O)4] in acid solutions of 4N to 9N LiCl. The results were compared with those obtained by measuring the faradaic impedance and with the results of the method of periodically changed rectangular voltage.
Mit 7 Abbildungen 相似文献
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The standard enthalpies and (in part) free energies and entropies of transfer from amine (L) to amine + diluent (D) mixtures have been determined for MX2L2 complexes at 25°C using chloroform, 1,1,2,2,-tetrachloroethane (TCE), benzene, chlorobenzene, and ethyl acetate as diluents (M=Co and Zn; X=Cl and Br; L = pyridine, -picoline, and -picoline). Thermodynamic functions of transfer indicate specific outer-sphere interactions of the complexes with amine and protic diluents (chloroform and TCE) and reveal solvent-solvent interactions of amine + protic diluent mixtures. The effects of the nature of X, L, and M of the MX2L2 complexes on their interaction with the components of the mixed solvent are discussed.Deceased. 相似文献
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The osmotic and activity coefficients of aqueous sodium and potassium methyl sulfates have been determined at 25°C by the isopiestic method, in the molality range from ca.0.2 to 25 and 19 mol-kg–1, respectively. The results have been discussed in terms of the ion–ion and ion–water interactions on the basis of the Pitzer and Mayorga model and a method developed in our laboratory. 相似文献
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Constant current chronopotentiometric peak H at mercury electrodes was recently shown as a sensitive tool for global and local changes in protein conformation [1]. Large differences between the heights of peak H of native (hBSAnat) and denatured BSA (hBSAden) were observed. The ratio hBSAden/hBSAnat increased with more negative stripping current suggesting that the rate of potential change is important for discrimination between native and denatured BSA. Voltammetric peaks of BSA were less well developed and BSAden/BSAnat was much smaller. It was not possible to discriminate BSAden and BSAnat using carbon electrodes. 相似文献
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Ĺubor Fišera Volker Jäger Libuše Jarošková Juraj Kuban Vladimír Ondruš 《Chemistry of Heterocyclic Compounds》1995,31(10):1180-1182
The title reaction was investigated for both known achiral and new chiral optically pure nitrones. In all cases, formation of only two diastereomeric cycloadducts was observed.Department of Organic Chemistry, Slovak Technical University, 812 37 Bratislava, Slovak Republic. Department of Organic Chemistry, University of Stuttgart, D-70569 Stuttgart, Germany. Published in Khimiya Geterotsiklicheskikh Soedinenii No. 10, pp. 1350–1352. October, 1995. Original article submitted August 24, 1995. 相似文献
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Thermodynamic characteristics for the 1:1 complex formation reactions ofp-nitrophenol with amines in benzene, chlorobenzene, ando-dichlorobenzene have been derived from combined spectrophotometric equilibrium constant determinations and calorimetric measurements. For cyclohexane as the reaction medium, approximate values of the reaction heats have been calculated from temperature dependences of the equilibrium constants. The results are analyzed in terms of the separately determined heats of transfer of the reactants between the solvents used. Usingp-nitrophenol andp-fluoronitrobenzene as reference compounds, the hydrogen-bond-type interactions ofp-nitrophenol with the aromatic solvents are shown to be accompanied by other specific interactions of comparable strength. 相似文献