FG Physikalische Chemie / Molekulare Materialwissenschaften

39 Items

Recent Submissions
Preparation of Reinforced Anisometric Patchy Supraparticles for Self‐Propulsion

Oguztürk, H. Esra ; Bauer, Leona J. ; Mantouvalou, Ioanna ; Kanngieβ  er, Birgit ; Velev, Orlin D. ; Gradzielski, Michael (2021-05-05)

The preparation of fumed silica‐based anisometric supraparticles with well‐defined catalytically active patches suitable for self‐propulsion is presented here. These sub‐millimeter‐sized particles can self‐propel as they contain Pt‐covered magnetite (Fe3O4) nanoparticles, where the Pt can decompose catalytically a “fuel” like H2O2 and thereby propel the supraparticles. By their magnetic propert...

Functionalized peptide hydrogels as tunable extracellular matrix mimics for biological applications

Hellmund, Katharina S. ; von Lospichl, Benjamin ; Böttcher, Christoph ; Ludwig, Kai ; Keiderling, Uwe ; Noirez, Laurence ; Weiß, Annika ; Mikolajczak, Dorian J. ; Gradzielski, Michael ; Koksch, Beate (2020-10-26)

The development of tailorable and biocompatible three‐dimensional (3D) substrates or molecular networks that reliably mimic the extracellular matrix (ECM) and influence cell behavior and growth in vitro is of increasing interest for cell‐based applications in the field of tissue engineering and regenerative medicine. In this context, we present a novel coiled coil‐based peptide that self‐assemb...

A simple extension of the commonly used fitting equation for oscillatory structural forces in case of silica nanoparticle suspensions

Schön, Sebastian ; Klitzing, Regine von (2018-04-05)

Background: The ordering of molecules or particles in the vicinity of a confining surface leads to the formation of an interfacial region with layers of decreasing order normal to the confining surfaces. The overlap of two interfacial regions gives rise to the well-known phenomenon of oscillatory structural forces. These forces are commonly fitted with an exponentially decaying harmonic oscilla...

Externally triggered oscillatory structural forces

Schön, Sebastian ; Richter, Marcel ; Witt, Marcus ; Klitzing, Regine von (2018-09-04)

This paper addresses triggering of oscillatory structural forces via temperature variation across an aqueous dispersion of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) nanogels confined between silica surfaces. Oscillatory structural forces are a well-known phenomenon in colloidal science, caused by interactions between molecules or colloids. Modulation of these forces usually requires...

A temperature-controlled electric field sample environment for small-angle neutron scattering experiments

Hayward, Dominic W. ; Magro, Germinal ; Hörmann, Anja ; Prévost, Sylvain ; Schweins, Ralf ; Richardson, Robert M. ; Gradzielski, Michael (2021-03-08)

A new sample environment is introduced for the study of soft matter samples in electric fields using small-angle neutron scattering instruments. The sample environment is temperature controlled and features external electrodes, allowing standard quartz cuvettes to be used and conducting samples or samples containing ions to be investigated without the risk of electrochemical reactions occurring...

Structural control in micelles of alkyl acrylate-acrylate copolymers via alkyl chain length and block length

Azeri, Özge ; Schönfeld, Dennis ; Noirez, Laurence ; Gradzielski, Michael (2020-06-02)

Amphiphilic copolymers with poly (alkyl acrylate) as hydrophobic and poly (acrylic acid) (AA) as hydrophilic block have been synthesised. The alkyl chain was varied from butyl to dodecyl, thereby varying systematically the polarity of the hydrophobic block whose length was between 35 and 70, while the PAA block had ~ 100 units. Such relatively short amphiphiles should equilibrate quickly in aqu...

Dynamics in polyelectrolyte/microemulsion complexes

Simon, Miriam ; Gradzielski, Michael ; Hoffmann, Ingo (2020-08-20)

Oil-in-water (O/W) microemulsion droplets are convenient carriers for hydrophobic molecules in an aqueous phase and are used for a wide range of applications. We studied weakly charged O/W microemulsion droplets complexed with oppositely charged polyacrylates that form long linear arrangements of droplets. All samples showed rather low viscosities, which is in contrast to similar systems of hyd...

PyDSC: a simple tool to treat differential scanning calorimetry data

Cisse, Aline ; Peters, Judith ; Lazzara, Giuseppe ; Chiappisi, Leonardo (2020-05-16)

Herein, we describe an open-source, Python-based, script to treat the output of differential scanning calorimetry (DSC) experiments, called pyDSC , available free of charge for download at https://github.com/leonardo-chiappisi/pyDSC under a GNU General Public License v3.0. The main aim of this program is to provide the community with a simple program to analyze raw DSC data. Key features includ...

Solvothermal Synthesis of Lanthanide‐doped NaYF4 Upconversion Crystals with Size and Shape Control: Particle Properties and Growth Mechanism

Sun, Chunning ; Schäferling, Michael ; Resch‐Genger, Ute ; Gradzielski, Michael (2020-12-28)

Lanthanide‐doped NaYF4 upconversion nano‐ and microcrystals were synthesized via a facile solvothermal approach. Thereby, the influence of volume ratios of ethylene glycol (EG)/H2O, molar ratios of NH4F/RE3+ (RE3+ represents the total amount of Y3+ and rare‐earth dopant ions), Gd3+ ion contents, types of activator dopant ions, and different organic co‐solvents on the crystal phase, size, and mo...

An efficient synthetic strategy for ligand-free upconversion nanoparticles

Sun, Chunning ; Simke, Jan Ron Justin ; Gradzielski, Michael (2020-08-12)

High-quality lanthanide-doped upconversion nanoparticles are generally synthesized by employing long-chain oleic acid as the ligand in the synthetic process, rendering them hydrophobic, and preferentially dispersed in nonpolar solvents. Thus, postsynthetic surface modifications are required prior to practical applications. Herein, we have developed a facile approach to remove the surface ligand...

Interaction of Proteins with a Planar Poly(acrylic acid) Brush: Analysis by Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D)

Walkowiak, Jacek ; Gradzielski, Michael ; Zauscher, Stefan ; Ballauff, Matthias (2020-12-30)

We describe the preparation of a poly(acrylic acid) (PAA) brush, polymerized by atom transfer radical polymerization (ATRP) of tert-butyl acrylate (tBA) and subsequent acid hydrolysis, on the flat gold surfaces of quartz-crystal microbalance (QCM) crystals. The PAA brushes were characterized by Fourier transform infrared (FT-IR) spectroscopy, ellipsometry and water contact angle analysis. The i...

Effect of the supramolecular interactions on the nanostructure of halloysite/biopolymer hybrids: a comprehensive study by SANS, fluorescence correlation spectroscopy and electric birefringence

Cavallaro, Giuseppe ; Chiappisi, Leonardo ; Gradzielski, Michael ; Lazzara, Giuseppe (2020-03-16)

The structural properties of halloysite/biopolymer aqueous mixtures were firstly investigated by means of combining different techniques, including small-angle neutron scattering (SANS), electric birefringence (EBR) and fluorescence correlation spectroscopy (FCS). Among the biopolymers, non-ionic hydroxypropylcellulose and polyelectrolytes (anionic alginate and cationic chitosan) were selected....

Oscillatory structural forces

Schön, Sebastian (2020)

The focus of this thesis is on the investigation of the ordering of nanoparticles in a geometric confinement between two outer surfaces at variable separations and the resulting forces acting on said surfaces, namely the oscillatory structural forces. At the beginning salt free aqueous suspensions of silica nanoparticles at varying concentrations are investigated via colloidal probe atomic fo...

Interaction of proteins with multivalent polyelectrolytes

Walkowiak, Jacek (2020)

In the present work the thermodynamics of protein adsorption to charged polyelectrolytes is explored. Unravelling interactions of proteins with highly charged polyelectrolytes as e.g. DNA is a central topic in biophysics since many years. It is now well-established that ionic interactions play a major role for the strength of binding as expressed through the thermodynamic binding constant Kb. M...

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...