Search

Die Antifouling-Wirkung von piezoelektrischen Filtrationsmembranen gilt in der Membrantechnik als ein vielversprechender Ansatz, um Verschmutzungen der Membranoberflächen während der Filtrationsprozesse zuvorzukommen und die Filtrationsleistung zu steigern. Hierzu wird die Eignung einer elektrogesponnenen Mikrofiltrationsmembran aus dem piezoelektrischen Copolymer Poly(vinylidenfluorid-co-trifluorethylen) evaluiert. Maßgeblich für die piezoelektrische Phasenbildung und den resultierenden Eigenschaften der Polymerlösung für die Membranherstellung im Elektrospinnprozess ist der Einfluss von Lösemitteln und -gemischen. Durch die Untersuchung der Löslichkeitsparameter des Copolymers werden gezielt Lösemittelkombinationen und Volumenverhältnisse variiert, um deren Auswirkungen auf die Bildung des piezoelektrischen Beta-Phasenanteils zu analysieren. Zur Bestimmung der Membran-Resonanzfrequenz werden Vibrometermessungen genutzt. Diese Frequenz ist ausschlaggebend zur piezoelektrischen Anregung der Membran und damit zur Realisierung einer Antifouling-Wirkung. Die anschließende Überprüfung von leistungssteigernden Filtrationsmaßnahmen erfolgt über die transportspezifische Charakterisierung des Transmembranfluxes und –drucks in einem zur piezoelektrischen Anregung konstruierten Dead-End-Filtrationssystem durch Filtrationsversuche mit und ohne angelegte Wechselspannung., In membrane technology, the antifouling-effect of piezoelectric filtration membranes to increase filtration performance is promising. It could reduce fouling of membrane surfaces during filtration processes. This thesis evaluates the effectiveness of an electrospun microfiltration membrane made from piezoelectric copolymer poly(vinylidene fluoride-co-trifluoroethylene). The influence of solvents and solvent mixtures is relevant for the piezoelectric phase formation and the resulting properties of the polymer solution for membrane production in the electrospinning process. Through studying the solubility parameters of copolymer, the impact that all these parameters have on the formation of the piezoelectric beta phase fraction is specifically analysed. Vibrometer measurements are used to determine the membrane resonance frequency. This frequency is crucial for optimising the piezoelectric oscillation of the membrane, and is therefore critical in order to achieve the desired antifouling-effect. The subsequent verification of filtration performance enhancements is conducted using transport-specific characterisation of the transmembrane flux and pressure. This is done in a dead-end filtration system designed for piezoelectric actuation through filtration experiments with and without alternating voltage.

Polymeric materials are widely employed for monitoring volatile organic compounds (VOCs). Compared to other sensitive materials, polymers can provide a certain degree of selectivity, based on their chemical affinity with organic solvents. The addition of conductive nanoparticles within the polymer layer is a common practice in recent years to improve the sensitivity of these materials. However, it is still unclear the effect that the nanoparticles have on the selectivity of the polymer membrane and vice versa. The current work proposes a methodology based on the Hansen solubility parameters, for assessing the selectivity of both pristine and hybrid polymer nanocomposites. The impedance response of thin polydimethylsiloxane (PDMS) films is compared to the response of hybrid polymer films, based on the addition of multi-walled carbon nanotubes (MWCNTs). With the addition of just 1 wt.% of MWCNTs, fabricated sensors showcased a significant improvement in sensitivity, faster response times, as well as enhanced classification of non-polar analytes (>22% increase) compared to single PDMS layers. The methodology proposed in this work can be employed in the future to assess and predict the selectivity of polymers in single or array-based gas sensors, microfluidic channels, and other analytical devices for the purpose of VOCs discrimination., Peer Reviewed, Postprint (published version)

Hypothesis: Capillary suspensions feature networks of particles connected by liquid bridges, which are obtained by adding a small amount of a second immiscible liquid to a suspension. It is possible to link the network formation as well as the rheological behaviour of capillary suspensions to the intermolecular interactions of their constituents. Experiments and simulations: Through a combination of experimental and numerical methods, we present a novel approach, based on Hansen solubility parameters computed from Molecular Dynamics (MD) simulations, to rationalize and predict the rheological behaviour of capillary suspensions. We investigated the formation of capillary suspensions for various combinations of bulk and secondary liquids mixed with hydrophilic silica particles. The predictions were confirmed experimentally by rheological analysis, interfacial tension measurements and microscopy (CLSM) imaging. Findings: Numerical and experimental results show that the Hansen solubility parameters theory allows to predict the formation of capillary suspensions, whose strength exponentially decays with decreasing intermolecular interactions between the secondary liquids and the dispersed particles. High immiscibility between the bulk and secondary liquid strengthens the gel up to a critical immiscibility point, above which the strength of the gel remains mostly affected by the affinity between the secondary liquids and the dispersed particles. Furthermore, we find that hydrogen-bonding and polar interactions control the formation of capillary suspensions. This simple approach can guide the selection of adequate solvents and immiscible secondary liquids, allowing an easy formulation of new particulate-based gels.

Advances related to the use of solubility parameters and free energy theory for the phase behaviour study of polymer-modified bitumen (PMB) are reviewed in this paper. The origin and effects of PMB phase behaviour are criticised with a focus on PMB storage stability, morphology and swelling ratio. An overview of the solubility approach for studying PMB is given regarding the historical and future developments. Free energy expressions for PMB systems are analysed, including the free energy of mixing, elastic free energy and gradient energy. The kinetic aspects are discussed with respect to the diffusion and flow processes. It is indicated that the solubility bodies in the three-dimensional Hansen space and their degree of intersection can be useful for analysing the PMB thermodynamic equilibrium and thus storage stability. But they give no indication by themselves on the PMB morphology. With solubility parameters linked to the PMB free energy, however, an integrated thermodynamic approach can assist in understanding both PMB storage stability and morphology comprehensively. Due to the chemical complexity of bitumen and certain modifiers, the solubility body centres and radiuses should be both considered for a proper expression of the polymer-bitumen interaction in PMB. A hypothetical dilution process can simplify this process, but with limitations. The introduction of elastic free energy may lead to a new and more realistic expression of free energy for PMB system. With this overview, it is expected that a preliminary foundation is established towards a comprehensive and realistic thermodynamic framework for interpreting and predicting PMB phase behaviour., QC 20191028

In this work, the ability of several solvents to induce gel formation from amylomaize starch solubilized in dimethyl sulfoxide (DMSO) was investigated. The formed gels were subjected to solvent exchange using ethanol and dried with supercritical carbon dioxide (sc-CO2) to obtain the aerogels. The influence of starch concentration (3–15 wt%) and solvent content (20–80 wt%) on gel formation was also studied. It was demonstrated that the gelation of starch in binary mixtures of solvents can be rationalized by Hansen Solubility Parameters (HSP) revealing a crucial hole of hydrogen bonding for the gel’s strength, which is in agreement with rheological measurements. Only the addition of water or propylene glycol to starch/DMSO solutions resulted in strong gels at a minimum starch and solvent content of 7.5 wt% and 50 wt%, respectively. The resulting aerogels showed comparably high specific surface areas (78–144 m2 g−1) and low envelope densities (0.097–0.203 g cm−3). The results of this work indicate that the HSP parameters could be used as a tool to guide the rational selection of water-free gelation in starch/DMSO systems. In addition, it opens up an attractive opportunity to perform starch gelation in those solvents that are miscible with sc-CO2, avoiding the time-consuming step of solvent exchange., In this work, the ability of several solvents to induce gel formation from amylomaize starch solubilized in dimethyl sulfoxide (DMSO) was investigated. The formed gels were subjected to solvent exchange using ethanol and dried with supercritical carbon dioxide (sc-CO2) to obtain the aerogels. The influence of starch concentration (3–15 wt%) and solvent content (20–80 wt%) on gel formation was also studied. It was demonstrated that the gelation of starch in binary mixtures of solvents can be rationalized by Hansen Solubility Parameters (HSP) revealing a crucial hole of hydrogen bonding for the gel’s strength, which is in agreement with rheological measurements. Only the addition of water or propylene glycol to starch/DMSO solutions resulted in strong gels at a minimum starch and solvent content of 7.5 wt% and 50 wt%, respectively. The resulting aerogels showed comparably high specific surface areas (78–144 m2 g−1) and low envelope densities (0.097–0.203 g cm−3). The results of this work indicate that the HSP parameters could be used as a tool to guide the rational selection of water-free gelation in starch/DMSO systems. In addition, it opens up an attractive opportunity to perform starch gelation in those solvents that are miscible with sc-CO2, avoiding the time-consuming step of solvent exchange.

To facilitate industrial applications, as well as for environmental and health purposes, there is a need to find less hazardous solvents for processing the photoactive layer of organic solar cells. As there are vast amounts of possibilities to combine organic solvents and solutes, it is of high importance to find paths to discriminate among the solution chemistry possibilities on a theoretical basis. Using Hansen solubility parameters (HSP) offers such a path. We report on some examples of solvent blends that have been found by modelling HSP for an electron donor polymer (TQ1) and an electron acceptor polymer (N2200) to match solvent blends of less hazardous solvents than those commonly used. After the theoretical screening procedure, solubility tests were performed to determine the HSP parameters relevant for the TQ1:N2200 pair in the calculated solvent blends. Finally, thin solid films were prepared by spin-coating from the solvent blends that turned out to be good solvents to the donor-acceptor pair. Our results show that the blend film morphology prepared in this way is similar to those obtained from chloroform solutions.

The solubility parameter (SP) of a solvent is a key property that measures the polarity and quantifies the ‘like-dissolves-like’ principle, which is an important rule in chemistry for screening solvents for separation processes. It is challenging to experimentally obtain solubility parameters of non-volatile solvents like ionic liquids (ILs), deep eutectic solvents (DESs), and polymers. Here, Molecular Dynamics (MD) simulations have been used to compute the Hildebrand and Hansen solubility parameters of DESs, which are green solvents with potential applications in many different fields. The results from MD simulations are compared with limited available experimental data and commonly used SP correlations for non-volatile solvents. Very limited information is available in literature for the vapor phase composition of DESs. Solubility parameters are computed based on the vaporization of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) components of the DESs as well as clusters, consisting of HBD and HBA components. The relatively large SPs computed from MD indicate that the investigated choline chloride-based DESs are polar solvents. The values of SPs are not significantly affected by temperature. A comparison of vaporization enthalpies of HBD, HBA and clusters from the DES mixture suggests that it is more likely for HBD molecules to vaporize from the DES mixture and dominate the vapor phase., Accepted Author Manuscript, Engineering Thermodynamics

The authors wish to make the following correction to their paper [1].[...], The authors wish to make the following correction to their paper [1].[...]

This study aims at providing a model for the internal mixing energy of two liquids. The concerned variables are the solute molar volume V (cm3/mol.), the cohesion parameters and the Drago's parameters. The model is based on the following fundamental novelties: The fragmentation of molar cohesive energy ∆Ecoh (kJ/mol) into two distinct categories. Indeed, the dispersive and polar cohesion energies are magnetic and electrical in nature, and the cohesive energy of the chemical bonds (Hydrogen Bond) is due to charge transfer and orbital overlap. The origins of these two categories of energy are different, requiring two different treatments in use. For the first time, a relationship has been established between the cohesive energy from chemical bonds ∆Eh (kJ/mol) and Drago's parameters Ea, Eb, Ca, and Cb (KJ1/ 2mol-1/2). A simple equation has been proposed for the salvation energy of a gaseous solute in a liquid solvent. This equation contains a term for the perturbation energy of the solvent in the presence of the solute, namely the cavity formation energy, and different types of interaction energies between the solvent and the solute at infinite dilution. Based on calorimetric data published, the proposed model is compared with the classic model in terms of the mixing energy. The result shows a clear advantage of the new model over the old or conventional one. Clearly, this new model should provide a new method to determine the interaction parameters or interaction capacities of complex pharmaceutical molecules using a series of simple and well-chosen solvents.

Many small molecules can self-assemble into long fibers and thereby gel organic liquids. However, no capability exists to predict whether a molecule in a given solvent will form a gel, a thin solution (sol), or an insoluble precipitate. In this thesis, we build a framework for gelation via a common gelator based on Hansen solubility parameters (HSPs). Using HSPs, we construct 3-D plots showing regions of solubility (S), slow gelation (SG), instant gelation (IG), and insolubility (I) for DBS in different solvents. Our central finding is that these regions radiate out as concentric shells. The distance (R0) from the central sphere quantifies the incompatibility between gelator and solvent. The elastic moduli of the gels increase with R0, while the time to gelation decreases with R0. Our approach can be used to design organogels of desired strength and gelation time by judicious choice of a solvent or a blend of solvents.

To study, develop and enable industrially feasible utilization of wood hydrolysates (WHs), a Hansen’s Solubility Parameter (HSP) model was developed. The model aims to design formulations based on WH for efficient oxygen barrier films and coatings. Analyses such as Position Annihilation Lifetime Spectroscopy (PALS) and oxygen permeability (OP) tests strongly supported the model., QC 20201116

The possibility to develop a solubility parameter scale, with the purpose of predicting the performance and help the selection of ILs, is here evaluated. For the estimation of solubility parameters infinite dilution activity coefficient data is used. The results allowed the identification of a curious behavior for the ILs that seem to present more than one solubility parameter acting as polar molecules in some situations and as non-polar molecules in others, depending on the medium. This behavior was confirmed by solubility measurements of [C4MIM][PF6] in solvent mixtures. The solubility parameters were alternatively estimated based on other properties, namely viscosities and enthalpies of vaporization, and the relation between the various sets of solubility parameters is discussed. The results obtained suggest that, given the complexity of IL molecules and their liquid phase, a one-dimensional solubility parameter scale able to characterize these fluids is not feasible.

In dieser Arbeit wird das neue Prinzip der „Selbstinkompatiblen Lösungsmittel“ vorgestellt. Es wird theoretisch abgeleitet, dass eine Mischung aus zwei Substanzen mit ungünstigen Wechselwirkungen bereitwillig eine weitere Substanz aufnehmen sollte, die diese ungünstigen Wechselwirkungen durch Verdünnen vermindert. Dies sollte umso stärker ausgeprägt sein, je ungünstiger die Wechselwirkungen zwischen den beiden ersten Substanzen sind. Da sich jedoch Substanzen mit sehr ungünstigen Wechselwirkungen physikalisch nicht mischen, entstand die Idee, diese Substanzen durch eine kovalente Bindung aneinander zu binden. Ein solches Molekül, das aus zwei inkompatiblen Hälften besteht, wird im Folgendem Selbstinkompatibles Lösungsmittel genannt. Die in dieser Arbeit gewählten Substanzen zeigen mäßige Inkompatibilität, deshalb ist ein Vergleich zwischen einfachen physikalischen Mischungen und kovalent verknüpften Molekülhälften noch möglich. Dieses Prinzip wird für binäre und ternäre Mischungen quantitativ berechnet und experimentell in drei Serien von Experimenten bestätigt: i) unter Verwendung von Lösungskalorimetrie und Bestimmung der Wechselwirkungsparameter zwischen Komponente 3 und einer bereits hergestellt physikalischen binären Mischung aus Komponente 1 und 2, ii) unter Verwendung von Lösungskalorimetrie und Bestimmung der Wechselwirkungsparameter zwischen Komponente 3 und den selbstinkompatiblen Losungsmitteln, die den in (i) gewählten Mischungen entsprechen und iii) aus der Sättigungslöslichkeit der Komponente 3 in den entsprechenden selbstinkompatiblen Lösungsmitteln. In diesen drei verschiedenen Messserien wird stets der gleichen Trend beobachtet: Die Selbstinkompatibilität eines Lösungsmittels begünstigt den Lösevorgang., In this thesis a new principle of Self Incompatible Solvent is introduced. It is shown theoretically that a preexisting mixture of two substances (compound 1 and 2) with unfavorable interactions will readily dissolve a third compound because it diminishes the unfavorable interaction between the compound 1 and 2 by dilution. This behavior should be the stronger the more unfavorable the interactions between compound 1 and 2 are. However, substances with strong unfavorable interactions will not mix. Therefore the idea pursued here is to enforce the desired preexisting mixture for example by linking compound 1 covalently to compound 2. Such a molecule that is composed of two incompatible parts is called Self Incompatible Solvent in this work. In this thesis examples of incompatible compounds that show moderate incompatibility are chosen, therefore it was possible to do a comparison between simple physical mixtures and covalently linked incompatible molecules. The theoretical prediction of the theory is compared with experiments. This principle is calculated quantitatively for binary and ternary mixtures and compared with the experimental results in three distinct series of experiments: i) by using solution calorimetry and calculation of the interaction parameters between compounds 3 and the preexisting binary mixture of compound 1 and 2, ii) by using solution calorimetry and calculation of the interaction parameters between compound 3 and the Self Incompatible Solvent that correspond to the mixtures used in (i) and iii) from the saturation solubility of compound 3 in the Self Incompatible Solvent. The results obtained from the theoretical prediction and these obtained from the three different series of experiments show the same trend: the self incompatibility of the solvent improves the dissolution process.

The aim of this study was to determine the miscibility of drug and excipient to predict if glass solutions are likely to form when drug and excipient are melt extruded. Two poorly water-soluble drugs, indomethacin and lacidipine, were selected along with 11 excipients (polymeric and non-polymeric). Estimation of drug/excipient miscibility was performed using a combination of the Hoy and Hoftzyer/Van Krevelen methods for Hansen solubility parameter calculation. Miscibility was experimentally investigated with differential scanning calorimetry (DSC) and hot stage microscopy (HSM). Studies were performed at drug/excipient ratios, 1:4, 1:1 and 4:1. Analysis of the glass transition temperature (Tg) was performed by quench cooling drug/excipient melts in the DSC. Differences in the drug/excipient solubility parameters of <7.0 MPa1/2 were predicted to indicate significant miscibility and, therefore, glass solution formation on melt extrusion. In comparison, differences of <10 MPa1/2 were expected to indicate a lack of miscibility and not form glass solutions when melt extruded. Experimentally, miscibility was shown by changes in drug/excipient melting endotherms and confirmed by HSM investigations. Experimental results were in agreement with solubility parameter predictions. In addition, drug/excipient combinations predicted to be largely immiscible often exhibited more than one Tg upon reheating in the DSC. Melt extrusion of miscible components resulted in amorphous solid solution formation, whereas extrusion of an 'immiscible' component led to amorphous drug dispersed in crystalline excipient. In conclusion, combining calculation of Hansen solubility parameters with thermal analysis of drug/excipient miscibility can be successfully applied to predict formation of glass solutions with melt extrusion.