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Burg auf Fehmarn, Germany

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Burg auf Fehmarn, Germany
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Eich A.,WEE Solve GmbH | Wolf B.A.,University Mainz
ChemPhysChem | Year: 2011

Based on early measurements of J. J. Hermans and co-workers (D. T. F. Pals, J. J. Hermans, Recl. Trav. Chim. Pays-Bas 1952, 71, 513-520; D. T. F. Pals, J. J. Hermans, J. Polym. Sci. 1950, 5, 733-734; D. T. F. Pals, J. J. Hermans, J. Polym. Sci. 1948, 3, 897-898), the present contribution demonstrates how primary data should be evaluated in order to obtain reliable intrinsic viscosities. This procedure yields detailed information on the changes of the intrinsic viscosities and of the corresponding viscometric interaction parameters caused by an increasing salinity of water. Both quantities decline from a maximum value in the pure solvent to a minimum value, which is approached in the limit of sufficiently high salt concentrations, and can be modeled quantitatively by means of a Boltzmann sigmoid. Particular attention is paid to the significance of results obtained by means of the method of isoionic dilution, proposed by J. J. Hermans and co-workers. Salty: A procedure is described that yields information on the changes of the intrinsic viscosities and of the corresponding viscometric interaction parameters caused by an increasing salinity of water. The picture shows the reduction of the intrinsic viscosity of sodium pectinate in aqueous solution (27 °C) caused by the addition of different amounts of NaCl to the solvent. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Xiong X.,Xiamen University | Xiong X.,Johannes Gutenberg University Mainz | Eckelt J.,WEE Solve GmbH | Wolf B.A.,Johannes Gutenberg University Mainz
Macromolecules | Year: 2012

The interaction of linear and of three-arm star polybutadiene (PB) with THF was studied in the temperature range between 25 and 55 °C. Information for dilute solution rests on light scattering experiments; Flory-Huggins interaction parameter π stem from vapor pressure measurements as a function of ψ, the volume fraction of polymer. Despite the minute divergence in the architecture, the second osmotic virial coefficients of the two PBs differ noticeably. The present work demonstrates that these disparities become much more pronounced as ψ increases and that they depend strongly on temperature. These findings are interpreted on the basis of an approach accounting for the effects of chain connectivity and for conformational changes of the components. In this manner it is possible to rationalize the observed complex dependencies π (ψ, T), and to relate these effects to the dissimilar free volumes of the polymers. © 2012 American Chemical Society.


Xiong X.,Xiamen University | Xiong X.,Johannes Gutenberg University Mainz | Wolf B.A.,Johannes Gutenberg University Mainz | Wolf B.A.,WEE Solve GmbH
Soft Matter | Year: 2014

Dilute solutions of the sodium salt of polystyrene sulfonic acid (PSS-Na) were measured viscometrically as a function of composition in aqueous solvents of different salinity, where the extra salt was either NaCl or CaCl2. Such experiments yield {η}, the generalized intrinsic viscosities (hydrodynamic specific volume) of the polyelectrolyte for arbitrary polymer concentrations, c. In the limit of infinite dilution {η} becomes identical to the intrinsic viscosity [η]. For NaCl {η} decreases monotonously with rising c, whereas maxima are passed in the case of CaCl2. Condensing c and the concentration of extra salt in the mixed solvent into a single variable enables the establishment of predictive master curves. The viscometrically observed changes in the spatial extension of the individual polymer coils are discussed in light of the corresponding thermodynamic information. © 2014 The Royal Society of Chemistry.


Antonov Y.,RAS Emanuel Institute of Biochemical Physics | Wolf B.A.,Johannes Gutenberg University Mainz | Wolf B.A.,WEE Solve GmbH
Langmuir | Year: 2014

The phase diagram of the system water/dextran (DEX)/BSA was measured as well as modeled. On the experimental side, cloud points were determined and the coexisting phases were analyzed. The theoretical calculations use an approach capable of describing solutions of chain polymers and of globular proteins with the same formalism. The required thermodynamic input comes from experiments concerning the binary subsystems, except for the polymer blend for which one interaction parameter had to be adjusted. Both sources of information yield the same essential features: the existence of a large composition area of immiscibility, starting from the subsystem DEX/BSA and extending well into the region of dilute polymer solutions. This range is subdivided into three sections: one two-phase area at high polymer content, a two-phase area at low polymer content, and a three-phase region located in between. Measured and calculated phase diagrams match qualitatively; the reasons for the quantitative discrepancies are being discussed. © 2014 American Chemical Society.


Bercea M.,Petru Poni Institute of Macromolecular Chemistry | Nichifor M.,Petru Poni Institute of Macromolecular Chemistry | Eckelt J.,WEE Solve GmbH | Wolf B.A.,Johannes Gutenberg University Mainz
Macromolecular Chemistry and Physics | Year: 2011

The central and unexpected conclusion that can be drawn from the present work is the absence of any fundamental qualitative differences in the solution behavior of charged and uncharged polymers. For both types of systems, it is possible tomodelthethermodynamicbehaviorbythesame approach, accounting explicitly for chain connectivity and conformational relaxation. Unless very special interactions are involved (as in the case of block copolymers[14]), only three system-specific parameters are required, where it is, inmostcases, possible to eliminate one of thembymeans of the interrelation shown in Figure 15. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Morariu S.,Petru Poni Institute of Macromolecular Chemistry | Eckelt J.,WEE Solve GmbH | Wolf B.A.,Johannes Gutenberg University Mainz
Macromolecular Chemistry and Physics | Year: 2011

Dextran and random dextran-based copolymers containing different molar fractions f of charged units are studied in aqueous solution and in the pure state. The specific volumes of the solutions decrease linearly with increasing weight fraction of the polymer. Extrapolation to the pure state yields information on the hypothetical liquid polymers, exhibiting a pronounced minimum at f-0.1. A similar dependence is also observed for the pure solid polymers; however, the specific volumes at low f are considerably larger and at high f are slightly smaller. These differences are discussed in terms of the non-equilibrium structures formed during sample preparation. The thermal expansivities of the solutions pass through a maximum at f-0.1. Light scattering shows that the thermodynamic quality of water has a minimum at f-0.1. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ghimici L.,Petru Poni Institute of Macromolecular Chemistry | Nichifor M.,Petru Poni Institute of Macromolecular Chemistry | Eich A.,WEE Solve GmbH | Wolf B.A.,Johannes Gutenberg University Mainz
Carbohydrate Polymers | Year: 2012

Viscosities of dilute polymer solutions were measured in capillary viscometers for samples varying in their fraction f of charged units from 0.00 to 0.90. The dependence of the logarithm of the relative viscosity on polymer concentration c is in all cases reproduced quantitatively by three characteristic parameters: [η], the intrinsic viscosity; B, a viscometric interaction parameter (related to the Huggins constant); [η], a parameter required only for polyelectrolytes at low concentrations of extra salt. In pure water [η] increases more than 80 times as the fraction f rises from zero to 0.90 and [η] starts from zero and goes up to ≈71 mL/g. Upon the addition of NaCl [η] decreases by at least one order of magnitude (depending on the value of f). The observed dependences of log [η] on log csalt can be modeled quantitatively by Boltzmann sigmoids. © 2011 Elsevier Ltd. All Rights Reserved.


Bercea M.,Petru Poni Institute of Macromolecular Chemistry | Nita L.-E.,Petru Poni Institute of Macromolecular Chemistry | Eckelt J.,WEE Solve GmbH | Wolf B.A.,Johannes Gutenberg University Mainz
Macromolecular Chemistry and Physics | Year: 2012

In contrast to all earlier work on that subject, measurements are performed at high dilution up to total polymer concentrations wpol of 0.5 wt%. Aqueous solutions of poly(2-vinylpyrid-inium-Br) and of poly(styrene sulfonate-Na) are only fully miscible if wpol < 0.02 wt%. Decomposition into two liquid phases is observed upon an increase in wpol, where the extension of the miscibility gap is considerably larger at 60 than at 25 °C. Viscosity measurements demonstrate that the formation of the polyelectrolyte complexes may take hours. The intrinsic viscosity of the polyanion turns out to be 20 times larger than that of the polycation and to be much more sensitive toward the addition of extra salt. The [η] values of the blend pass a minimum as a function of its composition. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA.


Eckelt A.,Johannes Gutenberg University Mainz | Eckelt J.,WEE Solve GmbH | Wolf B.A.,Johannes Gutenberg University Mainz
Macromolecular Rapid Communications | Year: 2012

A reliable method to decide whether two polymers A and B are miscible or incompatible would be very helpful in many ways. In this contribution we demonstrate why traditional procedures cannot work. We propose to use the intrinsic viscosities [η] of the polymer blends instead of the composition dependence of the viscosities as a criterion for polymer miscibility. Two macromolecules A and B are miscible because of sufficiently favorable interactions between the two types of polymer segments. For solutions of these polymers in a joint solvent, this Gibbs energetic preference of dissimilar intersegmental contacts should prevail upon dilution and lead to the formation of interpolymer complexes, manifesting themselves in deviations from the additivity of intrinsic viscosities. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wolf B.A.,Johannes Gutenberg University Mainz | Wolf B.A.,WEE Solve GmbH
Industrial and Engineering Chemistry Research | Year: 2013

The thermodynamic description of the systems specified in the title requires in general dissimilar theories. This contribution presents an approach that is capable of modeling all of them with a maximum of three adjustable parameters. The Ansatz starts from the Flory-Huggins theory and extends it in a 2-fold manner: The number of segments assigned to the solvent is no longer one but treated as an adjustable parameter to account for the differences in the molecular geometries and in the free volumes of the components. Furthermore, the modeling allows for effects resulting from ternary contacts of the solvent/polymer/polymer type. Examination of the acquired thermodynamic expressions by means of literature data (composition-dependent chemical potentials of the solvents) demonstrates their validity. Solutions of proteins and of linear or branched chainlike macromolecules require two adjustable parameters for the quantitative thermodynamic modeling; polyelectrolyte solutions necessitate a third one. © 2013 American Chemical Society.

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