Gabriele Sadowski

Technische Universität Dortmund, Dortmund, North Rhine-Westphalia, Germany

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Publications (144)227.04 Total impact

  • Nikola Gushterov, Ferruccio Doghieri, Gabriele Sadowski
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    ABSTRACT: The high importance of natural rubber (NR) for mankind was identified already in the beginning of the 19th century. After the discovery of the vulcanization process, NR became one of the most significant renewable materials with an annual production of about 11 billion tons at present. Recently, the so-called shape-memory natural rubber (SMNR) was discovered [1]. SMNR is a lightly cross-linked NR, which can be used to store energy and very high strains. The shape-memory properties are received due to strain-induced crystallization, which occurs by stretching the polymer during a programming procedure. Programmed SMNR samples are thus semi-crystalline and can be triggered by mechanical force, heat and even through contact with VOC (volatile organic compound) vapors. Quitmann et al. [2] showed that constrained, lightly cross-linked SMNR even generates a reversible stress response upon exposure to VOC vapors, which depends on VOC type and concentration. This can be applied e.g. as vapor detector, as long as the mechanical reaction of the SMNR can be related to a certain VOC type and concentration. This requires the vapor-liquid-equilibrium (VLE) data of constrained SMNR/VOC systems. In this work, VLEs of constrained and unconstrained SMNR/VOC systems were investigated at 293.15 K using a magnetic suspension balance. The measurements provide VOC equilibrium concentrations and diffusivity data. The different strains correspond also to different initial polymer crystallinities, which show a notable effect on the VLEs. VLE modeling was performed using the Perturbed-Chain Statistical Associating Fluid Theory (PC‑SAFT). To account for the influence of constant strain on the VLE, a Helmholtz-energy contribution was used that accounts for network elasticity. This contribution is based on the affine network theory with a correction for the finite extensibility of the polymer chains [3]. The solubility of the VOCs in the amorphous part of the semi-crystalline SMNR was modeled based on the assumption that the crystalline phase does not absorb any solvent. The crystallinity of SMNR samples for each strain investigated was estimated based on literature data. Using the modeling approach suggested by Minelli and De Angelis [4], it was possible to correctly describe the experimental VLE data. For that purpose it was assumed that the crystallites exert an isotropic stress on the amorphous phase, which leads to reduced solubility in comparison to a non-stretched (fully amorphous) sample. This stress is quantified as an additional thermodynamic pressure inside the polymer phase and called constraint pressure pc. pc was considered as adjustable parameter. This allowed for quantitatively describing VLEs of SMNR/VOC systems over a broad range of strains and VOC concentrations. References [1] F. Katzenberg, B. Heuwers, J. C. Tiller, Adv. Mater., 2011, 23, 1909-1911. [2] D. Quitmann, N. Gushterov, G. Sadowski, F. Katzenberg, J. C. Tiller, ACS Appl. Mater. Interfaces, 2013, 5, 3504-3507. [3] B. Miao, T. A. Vilgis, S. Poggendorf, G. Sadowski, Macromol. Theory Simul., 2010, 19, 414-420. [4] M. Minelli, M. G. De Angelis, Fluid Phase Equilibria, 2014, 367, 173-181.
    14 AIChE Annual Meeting; 11/2014
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    ABSTRACT: Layer melt crystallization is a highly selective method for the separation of narrow boiling mixtures which are difficult to separate with conventional separation techniques like distillation due to low driving forces. Contrawise, layer melt crystallization has the drawback of limited capacity due to the direct connection between crystal product and required cooled surface. Here, the combination of the high throughput distillation and highly selective layer melt crystallization into an integrated hybrid process can lead to enormous benefits. Since the separation efficiency of the crystallization is not predictable, it has to be described with empirical correlation. Here, studies from literature use strongly simplified correlations by e.g. assuming complete separation. This bears the serious risk of overestimating the efficiency of the hybrid process. Further, the effective post purification step sweating was not implemented into hybrid processes in studies from literature. This study fills this gap in literature. A distilliation/melt crystallization hybrid process is optimized by realistically describing crystallization separation efficiency and by implementing sweating. The required crystallization models are presented and experimentally validated. The optimization of the hybrid process is done with different modelling depths and the results underline impressively the importance of the adequate description of the crystallization separation efficiency.
    Chemical Engineering and Processing 11/2014; · 1.95 Impact Factor
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    ABSTRACT: The incorporation of poorly-soluble active pharmaceutical ingredients (APIs) into excipients (e.g. polymers) to formulate an amorphous solid dispersion is a promising strategy to improve the oral bioavailability of the API. The application of copolymer excipients allows access to combination of different monomers and thus to the design of excipients to improve solid-dispersion properties. In this work, the thermodynamic phase behavior of solid dispersions was investigated as function of API, type of monomers, and copolymer composition. The glass-transition temperatures and API solubilities in the solid dispersions of naproxen and indomethacin in polyvinyl pyrrolidone, polyvinyl acetate, and copolymers with different weight fractions of vinyl pyrrolidone and vinyl actetate were investigated. It could be shown that the thermodynamic phase behavior of API/copolymer solid dispersions is a function of monomer type and copolymer composition. This effect was also predicted by using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). The glass-transition temperature of the solid dispersions was calculated with the Gordon-Taylor equation.
    Molecular Pharmaceutics 10/2014; · 4.57 Impact Factor
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    C. Brandenbusch, C. Kress, G. Sadowski
    Chemie Ingenieur Technik 09/2014; 86(9). · 0.70 Impact Factor
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    I. Smirnova, G. Sadowski, S. Enders
    Chemie Ingenieur Technik 09/2014; 86(9). · 0.70 Impact Factor
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    ABSTRACT: In this work the electrolyte perturbed chain statistical associating fluid theory (ePC-SAFT) was applied to model aqueous two-phase systems (ATPS) containing combinations of polyethylene glycol dimethyl ether (PEGDME), polypropylene glycol (PPG) and three poly(ethylene glycol-co-propylene glycol) copolymers in combination with 12 different inorganic salts for temperatures ranging from 278 K to 333 K. For the polymer modeling, a copolymer approach was applied splitting the polymer in different segment types accounting for their different molecular interactions. Using this approach allows for quantitative modeling of phase properties of aqueous homopolymer and copolymer solutions. ATPS consisting of water, salt and one out of the five polymers were successfully modeled by using only one binary interaction parameter between each polymer segment type and each ion. Applying these parameter set, the influence of (co)polymer composition, polymer molecular weight, and temperature on the phase composition and phase densities could be modeled accurately.
    Fluid Phase Equilibria 08/2014; · 2.38 Impact Factor
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    ABSTRACT: The representation of liquid–liquid equilibria (LLE) in ternary systems composed by water, 1,4-dioxane and different grades of poly(lactic acid) (PDLLA and PLLA), has been addressed through the PC-SAFT equation of state (EoS), in which the scheme of induced association is used to represent the interaction between solvent (dioxane) and non-solvent (water). The model parameters devoted to the description of pure component properties, as well as those pertinent to the representation of thermodynamic behaviour of solvent/non-solvent mixtures, were tuned on the basis of specific pressure–volume–temperature (PVT) data for the corresponding systems. Only the binary parameters for polymer–solvent and polymer/non-solvent pairs were adjusted to obtain a useful representation of experimental LLE data for the ternary systems. A suitable description of the thermodynamic properties of ternary mixtures was obtained using temperature-independent binary interaction parameters in the range 25–80 °C, and the consistency of the approach in the entire composition range was verified against experimental solubility data specifically measured for the polymer/non-solvent pair. The model shows good ability in the description of the thermodynamic properties of the system and it represents a reliable tool for the prediction of LLE also at conditions different from those considered for its set-up. This approach thus represents a useful designing tool for processes, such as thermally induced phase separation (TIPS), used in the preparation of microporous polymeric scaffolds.
    Fluid Phase Equilibria 07/2014; 374:1–8. · 2.38 Impact Factor
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    ABSTRACT: So far, the electrolyte PC-SAFT equation of state developed in 2005 [Ind. Eng. Chem. Res. (2005) 44, 3355-3362] has been applied to model solution densities, vapor-liquid equilibria (VLE), liquid-liquid equilibria (LLE), and solid-liquid equilibria (SLE) of solutions containing electrolytes. For that purpose, two ion-specific parameters were used to characterize any ion: the diameter of the solvated ion and the dispersion-energy parameter between ion and solvent. Dispersion was only considered between ions and solvents. Considering the small number of adjustable parameters, this approach yielded acceptable results especially for low and moderate electrolyte concentrations. However, for high salt concentrations, a distinct deviation between modeled and experimental data was observed. In this work a new modeling approach is suggested that accounts explicitly also for dispersion interactions between anions and cations. This yields a much more precise description of electrolyte solutions at higher concentrations compared to original ePC-SAFT. With this new approach it is also possible to directly model weak electrolyte solutions without using an additional approach that accounts for ion-pair formation. The new approach for applying ePC-SAFT is now able to model phase equilibria (VLE, LLE, SLE) of ternary electrolyte solutions containing water, organic solvents, salts, and amino acids even at high salt concentrations in good agreement with experimental data.
    Chemical Engineering Research and Design 06/2014; · 1.93 Impact Factor
  • Anke Prudic, Yuanhui Ji, Gabriele Sadowski
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    ABSTRACT: To improve the bioavailability of poorly soluble active pharmaceutical ingredients (APIs), these materials are often integrated into a polymer matrix that acts as a carrier. The resulting mixture is called a solid dispersion. In this work, the phase behaviors of solid dispersions were investigated as a function of the API as well as of the type and molecular weight of the carrier polymer. Specifically, the solubility of artemisinin and indomethacin was measured in different poly(ethylene glycol)s (PEG 400, PEG 6000, and PEG 35000). The measured solubility data and the solubility of sulfonamides in poly(vinylpyrrolidone) (PVP) K10 and PEG 35000 were modeled using the perturbed-chain statistical associating fluid theory (PC-SAFT). The results show that PC-SAFT predictions are in a good accordance with the experimental data, and PC-SAFT can be used to predict the whole phase diagram of an API/polymer solid dispersion as a function of the kind of API and polymer and of the polymer's molecular weight. This remarkably simplifies the screening process for suitable API/polymer combinations.
    Molecular Pharmaceutics 05/2014; · 4.57 Impact Factor
  • Journal of Supercritical Fluids The 04/2014; · 2.73 Impact Factor
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    ABSTRACT: In this work the ePC-SAFT equation of state is applied to model aqueous two-phase systems (ATPS) containing polyethylene glycol (PEG) and one of 16 different inorganic salts at temperatures between 277.15 K and 333.15 K. To ensure an accurate modeling of thermodynamic properties in PEG containing solutions, a novel modeling approach for PEG is applied considering different molecular interactions of PEG chain segments and PEG end-group segments. Applying this approach, the influence of PEG molecular weight, kind of salt, pH, as well as of temperature on the phase split as well as on the densities of the two phases can be modeled accurately. The overall absolute average deviation of the concentrations of the phase-forming components obtained by ePC-SAFT is 2.25 wt%. Moreover, it could be shown that by applying ion-specific model parameters, ePC-SAFT is even capable of predicting ATPS which were not used for the parameter estimation.
    Fluid Phase Equilibria 04/2014; 368:91–103. · 2.38 Impact Factor
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    ABSTRACT: Generally reversible stimuli-responsive materials do not memorize the stimulus. In this study we describe an example in which stretched and constrained semi-crystalline polymer networks respond to solvent gases with stress and simultaneously memorize the concentration and the chemical nature of the solvent itself in their microstructure. This written solvent signature can even be deleted by temperature.
    Advanced Materials 03/2014; · 14.83 Impact Factor
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    ABSTRACT: The industrial application of ionic liquids (ILs) requires the knowledge of their physical properties and phase behavior. This work addresses the experimental determination of the vapor-liquid equilibria (VLE) of binary systems composed of water + imidazolium-based ILs. The ILs under consideration are 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium methanesulfonate and 1-butyl-3-methylimidazolium acetate, which allows the evaluation of the influence of the IL anion through the phase behavior. Isobaric VLE data were measured at 0.05 MPa, 0.07 MPa and 0.1 MPa for IL mole fractions ranging between 0 and 0.7. The observed increase in the boiling temperatures of the mixtures is related with the strength of the interaction between the IL anion and water. The Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was further used to describe the obtained experimental data. The ILs were treated as molecular associating species with two association sites per IL. The model parameters for the pure fluids and the binary interaction parameter k_ij between water and ILs were determined by a simultaneous fitting to pure-IL densities, water activity coefficients at 298.15 K and VLE data at 0.1 MPa. Pure-IL densities, water activity coefficients and VLE data were well described by PC-SAFT in broad temperature, pressure and composition ranges. The PC-SAFT parameters were applied to predict the water activity coefficients at infinite dilution in ILs and a satisfactory prediction of experimental data were observed.
    Industrial & Engineering Chemistry Research. 02/2014; 53(9):3737–3748.
  • Xiaoyan Ji, Christoph Held, Gabriele Sadowski
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    ABSTRACT: ePC-SAFT was used to model the gas solubility in ionic liquids (ILs). The gases under consideration were CO, H2, H2S and O2, and the imidazolium-based ILs studied were [Cnmim][Tf2N], [Cnmim][PF6] and [Cnmim][BF4] (n = 2, 4, 6 and 8). For the ePC-SAFT modeling, each IL was considered to be completely dissociated into a cation and an anion. Each ion was modeled as a non-spherical species exerting repulsive, dispersive and Coulomb forces. CO, H2 and O2 were modeled as non-spherical molecules exerting repulsive and dispersive forces, and H2S was modeled as a non-spherical, associating molecule. ePC-SAFT reasonably predicts the gas solubility in the considered gas/IL mixtures. In order to describe the experimental gas solubilities quantitatively in a broad temperature and pressure range, one ion-specific binary interaction parameter between the IL-anion and the gas was applied, which was allowed to depend linearly on temperature.
    Fluid Phase Equilibria 02/2014; 363:59–65. · 2.38 Impact Factor
  • Franziska S. Laube, Gabriele Sadowski
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    ABSTRACT: Liquid–liquid extraction is a potential separation process for the purification and isolation of pharmaceuticals. However, as considerable experimental effort is required to choose an adequate extractant, liquid–liquid extraction is rarely used in the pharmaceutical industry. By applying a thermodynamic model to predict the extraction behavior of pharmaceuticals, the experimental effort required to select a suitable extractant can be decreased substantially. This work demonstrates that PC-SAFT is able to predict the extraction behavior of pharmaceuticals based solely on solid solubility data of the pharmaceutical in pure solvents. Because these data are required for pharmaceutical licensing and registration, they are usually available. To demonstrate the power of the modeling tool, six ternary two-phase systems containing a pharmaceutical intermediate or its impurity were modeled with PC-SAFT. The modeling results for the extraction behavior of the two pharmaceuticals were found to be in good agreement with the experimental data.
    Industrial & Engineering Chemistry Research. 01/2014; 53(2):865–870.
  • Muhammad Umer, Katja Albers, Gabriele Sadowski, Kai Leonhard
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    ABSTRACT: We use highly accurate ab initio calculations of binding enthalpies and entropies of gas phase clusters of alcohols to demonstrate how they can be used to obtain association parameters for PC-SAFT. The thermochemical results demonstrate that cooperativity effects and state dependent cluster distributions cause a strongly varying average enthalpy and entropy per bond as function of temperature and density for alcohols. In contrast to this, the two association parameters of PC-SAFT lead to density independent bond enthalpy and entropy and are thus effective parameters. Therefore, we choose to compute the cluster distribution at a universal state point and show that the thus obtained association parameters can be used to reduce the number of adjustable parameters from 5 to 3 with only a marginal loss of accuracy for most of the studied systems, and even an estimation of thermodynamic properties without adjusted parameters is possible. The ab initio calculations suggest that the 2B association scheme is more appropriate for 1-alkanols than the 3B one.
    Fluid Phase Equilibria 01/2014; 362:41–50. · 2.38 Impact Factor
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    ABSTRACT: In this work thermodynamic properties of electrolyte/amino acid/water solutions were measured and modeled. Osmotic coefficients at 298.15 K were measured by means of vapor-pressure osmometry. Amino-acid solubility at 298.15 K was determined gravimetrically. Considered aqueous systems contained one of the four amino acids: glycine, L-/DL-alanine, L-/DL-valine, and L-proline up to the respective amino-acid solubility limit and one of 13 salts composed of the ions Li+, Na+, K+, NH4+, Cl−, Br−, I−, NO3−, and SO42− at salt molalities of 0.5, 1.0, and 3.0 mol · kg−1, respectively. The data show that the salt influence is more pronounced on osmotic coefficients than on amino-acid solubility. The electrolyte Perturbed-Chain Statistical Association Theory (ePC-SAFT) was applied to model thermodynamic properties in aqueous electrolyte/amino-acid solutions. In previous works, this model had been applied to binary salt/water and binary amino acid/water systems. Without fitting any additional parameters, osmotic coefficients and amino-acid solubility in the ternary electrolyte/amino acid/water systems could be predicted with overall deviations of 3.7% and 9.3%, respectively, compared to the experimental data.
    The Journal of Chemical Thermodynamics 01/2014; 68:1–12. · 2.30 Impact Factor
  • Elisabeth Schäfer, Gabriele Sadowski, Sabine Enders
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    ABSTRACT: This work focuses on modeling and experimental investigation of temperature dependent interfacial properties of binary DMF/n-alkane (C7, C10, C12) mixtures. The systems consisting of solvents with very different polarity show azeotropic behavior. New experimental vapor–liquid and liquid–liquid interfacial tension data are provided between 298.15 and 328.15 K using the drop volume method. The Perturbed Chain Polar Statistical Associating Fluid Theory (PCP-SAFT) equation of state was combined with the Density Gradient Theory (DGT) to calculate phase equilibria and interfacial properties. Modeling results are in good agreement with the corresponding experimental data. Thereby, the binary parameter βij within the DGT framework does not equal one. Investigating density and concentration profiles in the interface revealed characteristic trends which are related to the azeotropic behavior of the mixtures.
    Fluid Phase Equilibria 01/2014; 362:151–162. · 2.38 Impact Factor
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    ABSTRACT: In this work, Δ(R)g(+) values for the enzymatic G6P isomerization were determined as a function of the G6P equilibrium molality between 25°C and 37°C. The reaction mixtures were buffered at pH=8.5. In contrast to standard literature work, Δ(R)g(+) values were determined from activity-based equilibrium constants instead of molality-based apparent values. This yielded a Δ(R)g(+) value of 2.55±0.05kJmol(-1) at 37°C, independent of the solution pH between 7.5 and 8.5. Furthermore, Δ(R)h(+) was measured at pH=8.5 and 25°C yielding 12.05±0.2kJmol(-1). Accounting for activity coefficients turned out to influence Δ(R)g(+) up to 30% upon increasing the G6P molality. This result was confirmed by predictions using the thermodynamic model ePC-SAFT. Finally, the influence of the buffer and of potassium glutamate as an additive on the reaction equilibrium was measured and predicted with ePC-SAFT in good agreement.
    Biophysical Chemistry. 01/2014;
  • Alexander Nann, Christoph Held, Gabriele Sadowski
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    ABSTRACT: The liquid–liquid equilibria (LLE) of ternary 1-butanol/water/ionic liquid (IL) mixtures were measured and predicted. The LLE data were measured for ternary mixtures containing 1-butanol, water, and one of the following ILs: 1-decyl-3-methylimidazolium tetracyanoborate ([Im10.1]+[tcb]−), 4-decyl-4-methylmorpholinium tetracyanoborate ([Mo10.1]+[tcb]−), 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Im10.1]+[ntf2]−), and 4-decyl-4-methylmorpholinium bis(trifluoromethylsulfonyl)imide ([Mo10.1]+[ntf2]−). The LLE data were determined at atmospheric pressure for two different temperatures (308.15 and 323.15 K). To evaluate the application of the ILs studied to the extraction of 1-butanol from aqueous solutions, the 1-butanol distribution coefficients and selectivities were determined from the data. The perturbed-chain statistical associating fluid theory (PC-SAFT) was used for modeling. Previously published pure-component PC-SAFT parameters for the ILs [ J. Phys. Chem. B 2013, 117 (11), 3173−3185] were used for this purpose. The binary interaction parameters for 1-butanol/IL pairs were set to zero. The binary interaction parameters for 1-butanol/water and water/IL pairs were determined by fitting to the respective binary LLE data at various temperatures. Without introducing any additional parameters or refitting existing PC-SAFT parameters, the liquid–liquid equilibria of the ternary 1-butanol/water/IL mixtures were predicted and exhibited good agreement with the experimental data. Moreover, the very sensitive property distribution coefficient and the selectivity of 1-butanol were accurately predicted.
    Industrial & Engineering Chemistry Research. 12/2013; 52(51):18472–18481.

Publication Stats

498 Citations
227.04 Total Impact Points

Institutions

  • 2004–2014
    • Technische Universität Dortmund
      • • Faculty of Biochemical and Chemical Engineering
      • • Laboratory of Thermodynamics (TH)
      Dortmund, North Rhine-Westphalia, Germany
  • 2007
    • Saint Petersburg State University
      Sankt-Peterburg, St.-Petersburg, Russia
  • 1995–2004
    • Technische Universität Berlin
      • • Institut für Prozess- und Verfahrenstechnik
      • • Division of Chemical Engineering
      Berlin, Land Berlin, Germany