Chemie Ingenieur TechnikVolume 90, Issue 8 p. 1104-1104 Buchbesprechung Nanodispersions. Von T. F. Tadros. H. Rehage, H. Rehage Dortmund, DeutschlandSearch for more papers by this author H. Rehage, H. Rehage Dortmund, DeutschlandSearch for more papers by this author First published: 26 July 2018 https://doi.org/10.1002/cite.201870086AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume90, Issue8August 2018Pages 1104-1104 RelatedInformation

In a series of experiments we studied the deformation and orientation behaviour of microcapsules in simple shear flow. For a large number of capsules we observed folding processes which were induced by the bending resistance, by membrane pre-stresses or the mechanical asymmetry of the surrounding viscoelastic wall materials. Periodic oscillations of the inclination angle were detected for non-spherical particles. At low shear rates a tumbling motion occurred in which the capsule turned around its axis. A swinging mode at evaluated shear rates was accompanied by tank-treading motions, a rotation of the membrane around the capsule core. Between these two well-known motions we also observed an intermittent regime.

Bilberries (Vaccinium myrtillus L.) are reported to show preventive activities against inflammatory bowel diseases (IBD), colon cancer or degenerative disease such as Alzheimer's dementia. These findings are attributed to the antioxidative and anti-inflammatory activities of one of the main ingredients, the anthocyanins. However, anthocyanins are sensitive to environmental conditions, thus their bioavailability in the gastrointestinal tract is an important determinant of their in vivo activity. In the study reported here, the potential benefits of encapsulating an anthocyanin rich bilberry extract (BE) on anthocyanin stability were investigated. Non-encapsulated BE and three different BE loaded microcapsule systems were incubated anaerobically in intestinal fluid, namely ileostomy effluents from volunteers. After exposure to these media released anthocyanins were identified and quantified by HPLC with UV/VIS detection. A constant degradation of anthocyanins from BE was observed to 29.7% of the applied amount within 24 h. In contrast to this, encapsulation of anthocyanins lead to a constant liberation for at least 6 h of about 14.5 to 20.5% of the initial concentration of anthocyanins from the matrix. These results illustrate the ability of encapsulation to provide a constant (triggered) release of anthocyanins into the intestinal system, but in contrast to the non-encapsulated BE lower low amounts being liberated.

The beamline BL9 of DELTA (Dortmund ELecTron Accelerator) is a multi-purpose beamline operating in an energy range between 4 and 27 keV. A short overview of the beamline and the experimental endstation is given. Exemplarily three typical applications, namely x-ray diffraction from interfaces, small angle x-ray scattering under high hydrostatic pressure and fast x-ray reflectivity measurements, are discussed in some detail in order to demonstrate the capabilities of the beamline.

Abstract Vesicles can be found in many applications like drug delivery or as models for cell membranes. It is often necessary to produce vesicles which are easy to adjust in size and which can be filled with different types of ingredients. In this publication we used phase transfer techniques in to form well defined vesicles. The synthesis of these particles occurred in three different steps. First, a water phase was covered by an oil phase containing surfactants. A water-in-oil emulsion was then added to the oil phase. In the third step the phase transfer was stimulated by sedimentation or centrifugation processes. In a series of experiments we measured the vesicle sizes and encapsulation efficiencies. Giant vesicles, formed by sedimentation processes had typical sizes between 1–10 μm. Smaller vesicles between 100–500 nm were observed after centrifugation processes. With both methods we could produce vesicles with encapsulation amounts about 10%.

The interactions of nanoparticles with surfactants and polymers is important in many technical fields e.g. suspensions, emulsions and foams. The possibility of manipulating such systems from outside (e.g. by external forces) is an ambitious aim for the future. In this context, the incorporation of magnetic nanoparticles can be helpful because they provide a magnetic responsibility to the colloidal systems. The stability of such emulsions or foams is inferred by a number of key parameters: namely the bulk adsorption of surfactant onto the particles, the influence of surfactant on particle aggregation, the combined effect on system interfacial tension, and the role of interfacial elasticity and viscosity. We investigated the bulk interaction of magnetic nanoparticles (γ-Fe2O3) with different charged and uncharged surfactants by dynamic light scattering and zeta potential analysis. The influence of the particle/surfactant interaction on the interfacial properties was investigated by surface tension, surface rheological and X-ray reflection (XRR) measurements.

Gum acacia is commonly used as a natural emulsifier in the food industry, in particular for beverages and flavour oil emulsions, in cosmetic products, ink, etc.1 The polysaccharide backbone of Acacia gum is composed of (1→3)-linked β-galactopyranose monomers and (1→6)-linked galactopyranose side chains, terminated either by glucuronic acid or by 4-O-methylglucuronic acid residues. The protein component is covalently linked to the polysaccharide, forming arabinogalactan–protein complexes. The simultaneous presence of hydrophilic sugar residues and hydrophobic amino acids contributes to its ability to adsorb either at the air/water or the oil/water interfaces.

In a series of experiments, we studied the interfacial activity of aromatic aliphatic molecules with rigid gemini-like structures at the interface between toluene and water. These molecules, called clips and tweezers, have rigid central benzene or naphthalene spacer-units, each substituted with two polar groups as well as two rigid aromatic side walls. They can serve as host molecules and selectively bind a variety of electron-deficient aromatic and aliphatic guest molecules. In different experiments, we compared the interfacial tensions with the calculated hydrophilic-lipid-balance (HLB) values of these molecules. The measured interfacial tensions depend as much on the HLB values as on the geometric structure of the water insoluble molecules. The concentration dependence of the surface tension gave evidence for the formation of inverse micellar aggregates, which were formed in the oil phase above a well-defined value of the bulk concentration. The presence of aggregates in the organic liquid could also be investigated by dynamic light scattering measurements. We observed typical diameters of the inverse micellar aggregates in the order of 5.6 nm, and the critical micelle concentrations (cmc's) coincided well with the results of interfacial tension measurements. From the surface excess in the vicinity of the cmc, we calculated the space occupied by a single clip molecule on the self-assembled monolayer. The observed molecular surface area was in agreement with the effective molecular diameters of the molecules. In additional experiments, we could also show that complexes with aromatic guest molecules such as 1,2-4,5-tetracyanobenzene (TCNB) led to a reduction of the amphiphilic clip properties.

Nanoparticle materials are interesting candidates for the development of advanced materials with regard to magnetic, optic and electronic properties [1-3]. Because of the broad range of applications where nanoparticles are used for surface and interface modification a better knowledge about the arrangement of nanoparticles at these interfaces is of scientific interest. Thus, our study focuses on the adsorption of maghemite (γ-Fe2O3) nanoparticles at different gas/liquid interfaces. In order to study the effect of electrostatic interaction between the positively charged nanoparticles and the gas/ liquid interface differently charged Langmuir films (stearic acid, stearic alcohol and stearic amin) were prepared on the nanoparticle solution. Beside this, the adsorption of maghemite nanoparticles at the bare gas/water interface and at a laterally polymerized OTS (poly(organosiloxane)) network was studied.

This study focuses on the biomimetic formation and growth of thin iron oxide films under Langmuir monolayers. These coherent film structures were formed in the presence of different iron chloride solutions during the addition of an ammonia atmosphere. Stearic acid, stearyl amine and stearyl alcohol were used as film forming surfactants while the subphase contained FeCl2, FeCl3 or a mixture of both salts. The thin, coherent films consisted of X-ray amorphous iron oxide, hydroxide or oxyhydroxide. The films were studied by scanning electron microscopy, atomic force microscopy, X-ray diffraction, dynamic light scattering and surface potential measurements. Based on the experimental results we propose a growth mechanism that is guided by the formation of nanoparticles in the subphase and their assembly and aggregation underneath the Langmuir films.

The adsorption of \(\gamma\hbox{-}{\rm Fe}_2{\rm O}_3\) (maghemite) nanoparticles at the aqueous solution/gas interface was investigated by x-ray reflectivity. Two different concentrations (0.07 g/L and 0.7 g/L) were probed. The x-ray reflectivities indicate the adsorption of nanoparticles at the liquid surface for the highly concentrated solution, while no nanoparticle adsorption could be detected at the surface of the low concentrated solution within several hours. The vertical electron density profile of the high concentration solution/gas interface indicates the formation of a low ordered monolayer of nanoparticles occupying only 6% of the interfacial region.

Detailed investigations of interfacial crystallization procedures are important to understand the basic principles of biomineralization processes. These interfacial phenomena can also be used to form new types of biomimetic composite materials. In a series of experiments we studied the influence of Langmuir-monolayers on the formation of ultra-thin calcium carbonate films. We systematically compared experiments performed at the water surface with results obtained at the water/oil interface. For stearic acid monolayers formed at the pure water surface, we were able to observe densely packed dispersions of ultra-thin CaCO3 crystals, which were adsorbed below the surfactant membranes. We analyzed details of these structures by means of Brewster-angle-microscopy and other microscopic techniques. At the oil/water interface, however, we observed the formation of coherent, ultra-thin calcium carbonate films. These extended, two-dimensional crystalline structures were characterized by scanning electron microscopy, X-ray diffraction, and other techniques like interfacial-shear-rheology.

Viscoelastic surfactant solutions of mixtures of cetylopyridiniumchloride and sodiumsalicylate exhibit a complicated relaxation behavior in the semidilute regime, where the network starts to form. They show a stretched exponential relaxation which can be measured by rheological experiments. We measured the time-dependent relaxation of the shear stress in these systems by applying different step functions of shear strain at solutions with different counterion concentrations. The stretching exponent a decreases with decreasing counterion concentration. In the vicinity of the overlap concentration c*, we observe a critical exponent of 0.32 which is still derivated from the theoretical value of 0.25 for pure reptation, as predicted by the theory of M. Cates. The disagreement might be due to Coulomb interactions of the rodlike micelles, which were not taken into account by the theoretical considerations.

Molecular clips and tweezers are able to selectively bind electron-deficient aromatic and aliphatic substrates. By means of pressure-area isotherms and Brewster angle microscopy (BAM), the self-association process and phase behavior of dimethylene-bridged molecular clips and tetramethylene-bridged molecular tweezers each substituted with two acetoxy groups as polar head groups were investigated. In a series of experiments, we observed that the molecular surface area of the clips and tweezers only depended on the skeletal structure and not on the polar groups. The measured areas agreed with the effective molecular diameters of the molecules if the aromatic side walls of the clips or tweezers were assumed to be aligned perpendicularly to the water surface. We compared the phase behavior of the pure molecular clips and tweezers with that of the host-guest complexes of these molecules, which were formed with 1,2,4,5-tetracyanobenzene (TCNB) as the guest molecule. For the clips with a central benzene (I) and naphthalene spacer unit (II), the complex formation with TCNB had no measurable influence on the phase diagrams of the films. We observed, however, a dramatic difference in the BAM images and pi-A isotherms between the pure molecular tweezers III and its complex with TCNB (TCNB@III). In addition to the pi-A isotherms, we used the surface potential (V)-area (A) isotherms to compare the pure tweezers III with the corresponding complex (TCNB@III). There was a strong difference in the maximum surface potential value for the pure tweezers (450 mV) and that for the complex (300 mV). In additional experiments, we prepared LB layers of such molecules, which were investigated by fluorescence spectroscopy. In comparison to the pure tweezers III, a luminescence emission of charge-transfer (CT) origin was observed for the host-guest complex (TCNB@III) fixed on the solid substrate. It turned out that the spectra were in good agreement with the results observed in chloroform solution.

In this article, we present a detailed analysis of the dynamic properties of entangled solutions of semi-flexible, threadlike surfactant micelles. These aggregates were formed by self-association processes in aqueous solutions of cationic surfactants such as cetylpyridinium chloride (CPyCl) or cetyltrimethylammonium bromide (CTAB) after the addition of different amounts of sodium salicylate (NaSal). We performed dynamic light scattering (DLS) experiments in combination with rheological measurements in order to investigate the dynamic properties of these viscoelastic surfactant solutions. In all samples, we observed three distinct relaxation regimes: initial monoexponential decay, followed by a power-law behavior at intermediate observation times. A second monoexponential region was detected at very long times, and this terminal regime described the viscoelastic features of the samples. The fast decay mode was induced by local cooperative motions in the gellike network. The intermediate and slowest decay modes point to the existence of quasi-anomalous diffusion processes. These phenomena are characterized by linear-diffusion properties at long times, and they obeyed anomalous logarithmic slow-dynamics behavior at intermediate time zones. The anomalous diffusion properties at intermediate time scales can be induced by the bending motions of the rod-shaped micelles between two entanglement points. This regime, which was more extended at lower temperatures, was described by the power-law form of the correlation function. The power-law exponent depended on the chemical structure of the surfactants and the temperature. The power-law regime shifted toward earlier times as the gellike network evolved. The slowest mode of the correlation function coincided very well with the shear stress relaxation times of the three-dimensional, transient networks. We observed that the temperature dependence of the slowest mode followed Arrhenius laws. This result provides experimental evidence for thermally activated topological relaxation processes of random fluid phases. We obtained activation energies of approximately 30 kcal/mol, and these data coincided well with previously reported literature values, which were determined in similar surfactant solutions. Characteristic "screening lengths", over which viscous effects became important, could also be determined from the activation energy. The elastic modulus G0, calculated from the slowest mode of the correlation function, was in pretty good agreement with rheological data. The light-scattering spectra were consistent with the theoretical model of dynamical coupling of the concentration fluctuations to viscoelasticity. Since only minute sample volumes are required for advanced DLS experiments, this method to extract viscoelasticity is well suited for advanced studies of gellike biomaterials.

Calcium phosphate nanoparticles were prepared by precipitation from aqueous solution. A stable colloid was formed by coating with DNA. The properties of the colloidal dispersion can be adjusted by variation of the inorganic nanoparticles. In particular, the partial substitution of calcium by magnesium or aluminum led to stable dispersions of nanoparticles. By a multi‐step precipitation process, it is also possible to include DNA into the particles in order to protect it from intracellular biochemical degradation. The dispersions were analyzed by dynamic light scattering, zeta potential measurements, analytical ultracentrifugation, and transmission electron microscopy.

Polyalkylcyanoacrylate nanocapsules are being prepared using two different types of o/w-emulsions: a conventional emulsion generated by intensive stirring with a home-made device and a mini-emulsion produced by the action of ultrasonic dispersion, using the alkylcyanoacrylate monomer as a hydrophobic agent. The emulsions and the resulting nanocapsule dispersions are compared using various methods of physical characterization. The formation of solid capsules is indicated by solid state NMR spectra and atomic force microscopy. Differences between the results of both synthetic approaches are found in terms of particle size distribution, zeta potential and tendency towards particle agglomeration. Capsules prepared by ultrasound via the mini-emulsion pathway tend to be smaller and more monodisperse. Their zeta potential is negative with larger absolute values as compared to capsules obtained from conventional emulsions, leading to stronger repulsive interactions and a higher stability against capsule agglomeration.

Monolayers and thin films of Au-55 clusters, linked by different dithiol spacer molecules and by polymerization between functionalized ligands, were prepared and investigated by TEM and AFM. Due to spacer molecules of different lengths, the cluster-cluster distances could be varied from 1.3 up to 3.8 nm, enabling later investigations of electron transport processes in two dimensions. Film formation was carried out using either Langmuir-Blodgett techniques or spin-coating processes in the presence of the spacer molecules. Polymerization reactions between neighboured clusters in monolayers or thin films succeeded by the use of vinyl-substituted ligand molecules. (Vinyl)(8)Si8O11(OH)(2) and p-styryl-diphenylphosphine modified Au-55 clusters could be linked by light-induced polymerization via the vinyl functions.

We analyze the deformation and bursting process of nonspherical organosiloxane capsules in centrifugal fields. Measurements were performed in a commercial spinning-drop tensiometer at different values of tube rotation. A theoretical analysis of the mechanics of initially ellipsoidal elastic shells subjected to centrifugal forces is developed where the deformation of the capsule is predicted as a function of the initial geometry and membrane elastic properties. For different types of organosiloxane membranes the Poisson number varies between 0 and 0.9. This phenomenon points to a considerable reduction of the membrane thickness at the onset of mechanical stress. Membrane-breaking processes always initiated at one of the pole ends of the capsules. Such rupture processes can be interpreted in terms of the derived theoretical model.

Chemie Ingenieur TechnikVolume 77, Issue 3 p. 236-239 Wissenschaftliche Kurzmitteilung Darstellung nichtsphärischer Kapseln für die Lebensmittelindustrie† I. Schneeweiß, I. Schneeweiß Universität Dortmund, Lehrstuhl für Physikalische Chemie II, Otto-Hahn Straße 6, D-44221 Dortmund, GermanySearch for more papers by this authorH. Rehage Prof. Dr., H. Rehage Prof. Dr. [email protected] Search for more papers by this author I. Schneeweiß, I. Schneeweiß Universität Dortmund, Lehrstuhl für Physikalische Chemie II, Otto-Hahn Straße 6, D-44221 Dortmund, GermanySearch for more papers by this authorH. Rehage Prof. Dr., H. Rehage Prof. Dr. [email protected] Search for more papers by this author First published: 23 February 2005 https://doi.org/10.1002/cite.200407087Citations: 5 † Vortrag von I. Schneeweiß anlässlich der GVC-Fachausschusssitzung, 1./2. März 2004 in Golm. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume77, Issue3Special Issue: PartikeltechnologieMarch, 2005Pages 236-239 RelatedInformation