FG Physikalische Chemie / Molekulare Materialwissenschaften

25 Items

Recent Submissions
Formation and characterization of complexes of oppositely charged oil-in-water (O/W) microemulsion droplets and polyelectrolytes

Simon, Miriam (2020)

Oil-in-water (O/W) microemulsion droplets are thermodynamically stable liquid systems that allow to have a rather high content of hydrophobic material dispersed in aqueous solution, which otherwise could not be dissolved. Further, microemulsion droplets have a well-defined spherical structure with low polydispersity, which renders them good model colloids. In that context, mixtures of charged m...

Dynamics of microemulsions bridged with hydrophobically end-capped star polymers studied by neutron spin-echo

Hoffmann, Ingo ; de Molina, Paula Malo ; Farago, Bela ; Falus, Peter ; Herfurth, Christoph ; Laschewsky, André ; Gradzielski, Michael (2014-01-21)

The mesoscopic dynamical properties of oil-in-water microemulsions (MEs) bridged with telechelic polymers of different number of arms and with different lengths of hydrophobic stickers were studied with neutron spin-echo (NSE) probing the dynamics in the size range of individual ME droplets. These results then were compared to those of dynamicic light scattering (DLS) which allow to investigate...

On the mesoscopic origins of high viscosities in some polyelectrolyte-surfactant mixtures

Hoffmann, Ingo ; Farago, Bela ; Schweins, Ralf ; Falus, Peter ; Sharp, Melissa ; Prévost, Sylvain ; Gradzielski, Michael (2015-08-18)

Oppositely charged polyelectrolyte (PE) surfactant mixtures allow the control of rheological parameters of a solution even at fairly low concentrations. For example, addition of 0.3 wt. % of anionic surfactant to a 1 wt. % solution of the polycation JR 400 increases the viscosity by 4 orders of magnitude. Recently, we could show that this increase is related to the formation of mixed, rod-like ...

Thermodynamic Analysis of the Uptake of a Protein in a Spherical Polyelectrolyte Brush

Walkowiak, Jacek ; Lu, Yan ; Gradzielski, Michael ; Zauscher, Stefan ; Ballauff, Matthias (2019-11-07)

A thermodynamic study of the adsorption of Human Serum Albumin (HSA) onto spherical polyelectrolyte brushes (SPBs) by isothermal titration calorimetry (ITC) is presented. The SPBs are composed of a solid polystyrene core bearing long chains of poly(acrylic acid). ITC measurements done at different temperatures and ionic strengths lead to a full set of thermodynamicbinding constants together wit...

Structural control of polyelectrolyte/microemulsion droplet complexes (PEMECs) with different polyacrylates

Simon, Miriam ; Krause, Patrick ; Chiappisi, Leonardo ; Noirez, Laurence ; Gradzielski, Michael (2018-10-23)

The ionic assembly of oppositely charged polyelectrolyte–surfactant complexes (PESCs) is often done with the aim of constructing more functional colloids, for instance as advanced delivery systems. However, PESCs are often not easily loaded with a solubilisate due to intrinsic restrictions of such complexes. This question was addressed from a different starting point: by employing microemulsion...

One-step procedure for the preparation of functional polysaccharide/fatty acid multilayered coatings

Micciulla, Samantha ; Hayward, Dominic W. ; Gerelli, Yuri ; Panzarella, Alain ; von Klitzing, Regine ; Gradzielski, Michael ; Chiappisi, Leonardo (2019-06-04)

Soft, stratified, amphiphilic systems are recurrent motifs in nature, e.g., in myelin sheaths or thylakoid stacks, and synthetic analogues are increasingly being exploited in the areas of biocatalysis, biosensing, and drug delivery. The synthesis of such complex multilayered systems usually requires lengthy preparation protocols. Here, we demonstrate the formation of multilayered fatty acid/pol...

Progress, challenges, and opportunities in enhancing NOM flocculation using chemically modified chitosan: a review towards future development

Loganathan, Paripurnanda ; Gradzielski, Michael ; Bustamante, Heriberto ; Vigneswaran, Saravanamuthu (2019-11-12)

Natural organic matter (NOM) occurs ubiquitously in water bodies and this can greatly affect feed or raw water quality (taste, colour, odour, bacterial growth). Furthermore, it reduces the performance of the coagulation-based water treatment process. Because the NOM content and its chemical complexity are increasing throughout the world, the removal of NOM from water has become a major challeng...

Structure and dynamics of polyelectrolyte surfactant mixtures under conditions of surfactant excess

Hoffmann, Ingo ; Simon, Miriam ; Farago, Bela ; Schweins, Ralf ; Falus, Peter ; Holderer, Olaf ; Gradzielski, Michael (2016-09-22)

Oppositely charged polyelectrolyte (PE) surfactant mixtures can self-assemble into a large variety of mesoscopic structures, so-called polyelectrolyte surfactant complexes (PESCs). These structures directly affect the macroscopic behavior of such solutions. In this study, we investigated mixtures of the cationically charged PE JR 400 and the anionic surfactant SDS with the help of different neu...

Dynamics of small unilamellar vesicles

Hoffmann, Ingo ; Hoffmann, Claudia ; Farago, Bela ; Prévost, Sylvain ; Gradzielski, Michael (2018-03-12)

In this paper, we investigate the dynamics of small unilamellar vesicles with the aid of neutron spin-echo spectroscopy. The purpose of this investigation is twofold. On the one hand, we investigate the influence of solubilised cosurfactant on the dynamics of the vesicle’s surfactant bilayer. On the other hand, the small unilamellar vesicles used here have a size between larger vesicles, with d...

Structure, Dynamics, and Composition of Large Clusters in Polyelectrolyte–Surfactant Systems

Hoffmann, Ingo ; Simon, Miriam ; Bleuel, Markus ; Falus, Peter ; Gradzielski, Michael (2019-03-15)

Mixtures of oppositely charged polyelectrolyte (PE) and surfactant show rich structural behavior. The dynamics of such self-assembled structures can be quite complex. For example, using dynamic light scattering (DLS), we observed a slow collective relaxation mode for mixtures of the cationically charged PE JR 400 and the anionic surfactant SDS if the concentration of the system is sufficiently ...

Changes in Phase Behavior from the Substitution of Ethylene Oxide with Carbon Dioxide in the Head Group of Nonionic Surfactants

Spiering, Vivian Jeannette ; Ciapetti, Aurora ; Tupinamba Lima, Michelle ; Hayward, Diminic W. ; Noirez, Laurence ; Appavou, Marie-Sousai ; Schomäcker, Reinhard ; Gradzielski, Michael (2019-11-25)

Nonionic ethylene oxide (EO)‐based surfactants are widely employed in commercial applications and normally form gel‐like liquid crystalline phases at higher concentrations, rendering their handling under such conditions difficult. By incorporating CO2 units in their hydrophilic head groups, the consumption of the petrochemical EO was reduced, and the tendency to form liquid crystals was suppres...

The interaction of hydrogen with CeO2 (111)/Ru (0001) and surface action spectroscopy

Plucienik, Agata (2019)

The first part of this thesis describes the setup of an apparatus for vibrational surface action spectroscopy as well as first experiments with this new method employing infrared radiation from the free electron laser of the Fritz Haber Institute. Vibrational action spectroscopy has been used previously mostly for the characterization of clusters in the gas phase. We have extended this method t...

Neutralisation rate controls the self-assembly of pH-sensitive surfactants

Hayward, Dominic W. ; Chiappisi, Leonardo ; Teo, Jyh Herng ; Prévost, Sylvain ; Schweins, Ralf ; Gradzielski, Michael (2019-10-14)

The degree of ionisation of a weakly acidic surfactant can be continuously modified from nonionic to ionic by adjusting the pH. This property can be used to control the curvature and therefore the morphology of the self-assembled aggregates it forms in solution. Herein, we report the surprising phenomenon, observed in the alkyl ether oligo(ethylene oxide) carboxylate (CH3(CH2)11/13OEO4.5CH2COOH...

The interaction of soft Silica nanoparticles with phospholipid membranes

Bekir, Marek (2019)

In last decades, the study of the interaction between inorganic nanoparticles and phospholipid mem-branes gained more attention as it may enable new attractive application possibilities in nanomedicine. In this context vesicles composed of phospholipid membranes serve as a model for biological mem-branes. Furthermore, the interaction with more or less soft nanoparticles has a great relevance, a...

Synthesis and characterization of poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA) modified silica nanoparticles

Altin, Burcu (2019)

In this work, we described a multi-step route for preparation of a pH responsive polymer, 2-(dimethylamino) ethyl methacrylate (DMAEMA), grafted silica nanoparticles with a size of 10- 100 nm in diameter via surface initiated- atom transfer radical polymerization (SI-ATRP). We prepare as a starting point well-defined silica nanoparticles (SNPs) by means of amino acid-based catalysis (L-Arginine...

Structural Analysis of a Modern o/w-Emulsion Stabilized by a Polyglycerol Ester Emulsifier and Consistency Enhancers

Dahl, Verena ; Friedrich, Achim ; Meyer, Jürgen ; Venzmer, Joachim ; Belkoura, Lhoussaine ; Strey, Reinhard ; Mayer, Christian ; Michel, Raphael ; Gradzielski, Michael (2018-01-18)

The aim of our work was to study the structure of a typical modern cosmetic oil-in-water emulsion (o/w-emulsion), based on the emulsifier polyglyceryl-3 dicitrate/stearate and glycerylstearate/stearyl alcohol as consistency enhancer. We have used a systematic approach building up the cosmetic emulsion step by step, characterizing all systems by using Small Angle Neutron Scattering (SANS), Diffe...

Gels Obtained by Colloidal Self-Assembly of Amphiphilic Molecules

Malo de Molina, Paula ; Gradzielski, Michael (2017-08-03)

Gelation in water-based systems can be achieved in many different ways. This review focusses on ways that are based on self-assembly, i.e., a bottom-up approach. Self-assembly naturally requires amphiphilic molecules and accordingly the systems described here are based on surfactants and to some extent also on amphiphilic copolymers. In this review we are interested in cases of low and moderate...

Droplets, Evaporation and a Superhydrophobic Surface: Simple Tools for Guiding Colloidal Particles into Complex Materials

Sperling, Marcel ; Gradzielski, Michael (2017-05-04)

The formation of complexly structured and shaped supraparticles can be achieved by evaporation-induced self-assembly (EISA) starting from colloidal dispersions deposited on a solid surface; often a superhydrophobic one. This versatile and interesting approach allows for generating rather complex particles with corresponding functionality in a simple and scalable fashion. The versatility is base...

Controlling the formation of vesicle structures and their fixation by polymerization

Yalcinkaya, Hacer (2019)

In recent years, nanostructures have drawn much interest due to their potential applications in biomedicine, energy conversion, detergency or electronics. Controlling their formation and stability is one of the key issues to obtain such versatile structures with enhanced morphological properties. Especially vesicles are interesting nanostructures with their hollow spherical geometry, allowing e...

Facile Control over the Supramolecular Ordering of Selfassembled Peptide Scaffolds by Simultaneous Assembly with a Polysacharride

Li, Rui ; Boyd-Moss, Mitchell ; Long, Benjamin ; Martel, Anne ; Parnell, Andrew ; Dennison, Andrew J. C. ; Barrow, Colin J. ; Nisbet, David R. ; Williams, Richard J. (2017-07-06)

Enabling control over macromolecular ordering and the spatial distribution of structures formed via the mechanisms of molecular self-assembly is a challenge that could yield a range of new functional materials. In particular, using the self-assembly of minimalist peptides, to drive the incorporation of large complex molecules will allow a functionalization strategy for the next generation of bi...