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Recent Publications


Measurements of periodically perturbed dewetting force fields and their consequences on the symmetry of the resulting patterns

2021-rei-02.jpgWe studied the origin of breaking the symmetry for moving circular contact lines of dewetting polymer films suspended on a periodic array of pillars. There, dewetting force fields driving polymer flow were perturbed by elastic micro-pillars arranged in a regular square pattern. Elastic restoring forces of deformed pillars locally balance driving capillary forces and broke the circular symmetry of expanding dewetting holes. The observed envelope of the dewetting holes reflected the symmetry of the underlying pattern, even at sizes much larger than the characteristic period of the pillar array, demonstrating that periodic perturbations in a driving force field can establish a well-defined pattern of lower symmetry. For the presented system, we succeeded in squaring the circle. [more...]



Surface-modified elastomeric nanofluidic devices for single nanoparticle trapping

pfohl-02.jpgOur work focuses on the development of simpler and effective production of nanofluidic devices for high-throughput charged single nanoparticle trapping in an aqueous environment. Single nanoparticle confinement using electrostatic trapping has been an effective approach to study the fundamental properties of charged molecules under a controlled aqueous environment. Conventionally, geometry-induced electrostatic trapping devices are fabricated using SiOx-based substrates and comprise nanochannels imbedded with nanoindentations such as nanopockets, nanoslits and nanogrids. These geometry-induced electrostatic trapping devices can only trap negatively charged particles, and therefore, to trap positively charged particles, modification of the device surface is required. [more...]



Changes in Surface Free Energy and Surface Conductivity of Carbon Nanotube/Polyimide Nanocomposite Films Induced by UV Irradiation

am1c02654_0012.gifChanges in surface energy and electrical conductivity of polyimide (PI)-based nanocomposite films filled with carbon nanotubes (CNTs) induced by UV exposure are gaining considerable interest in microelectronic, aeronautical, and aerospace applications. However, the underlying mechanism of PI photochemistry and oxidation reactions induced by UV irradiation upon the surface in the presence of CNTs is still not clear. Here, we probed the interplay between CNTs and PIs under UV exposure in the surface properties of CNT/PI nanocomposite films.   [more...]


  
Continuous Illumination of a Conjugated Polymer Causes Strong Enhancement of Photoluminescence

jp1c01837_0009.jpgWe present measurements of absorbance and photoluminescence (PL) for films of poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) as a function of temperature (T) and time (t) of illumination. While having no detectable influence on absorbance of this conjugated polymer, our experiments clearly revealed that illumination of PDOPT caused a significant increase in the PL intensity (IPL(T,t)), that is, the emission probability of PDOPT. Without illumination, we always observed a decrease in IPL with time. An increase in IPL was only detectable when the sample was illuminated. [more...]



Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

brahim-polymers.jpgWe examined the formation of self-seeded platelet-like crystals from polystyrene-block-polyethylene oxide (PS-b-PEO) diblock copolymers in toluene as a function of polymer concentration (c), crystallization temperature (TC), and self-seeding temperature (TSS). We showed that the number (N) of platelet-like crystals and their mean lateral size (L) can be controlled through a self-seeding procedure.  [more...]



Formation of Stacked Three-Dimensional Polymer “Single Crystals”

ma1c00081_0006.gif

Stacks of crystalline lamellae all having a uniquely oriented hexagonal shape, referred to as “3D (three-dimensional) single crystals”, were obtained via isothermal crystallization of isotactic polystyrene at a temperature close to the melting point. The height of the stacks of lamellae reached several micrometers corresponding to hundreds of superposed lamellar crystals. We propose that the mechanism of self-induced nucleation allowed propagating the orientation of the basal lamellar crystal to all other lamellae in the stack. [more...]



Concepts of nucleation in polymer crystallization

2021-xujun.jpgNucleation plays a vital role in polymer crystallization, in which chain connectivity and thus the multiple length and time scales make crystal nucleation of polymer chains an interesting but complex subject. Though the topic has been intensively studied in the past decades, there are still many open questions to answer. The final properties of semicrystalline polymer materials are affected by all of the following: the starting melt, paths of nucleation, organization of lamellar crystals and evolution of the final crystalline structures. [more...]



Optimization of Nanofluidic Devices for Geometry‐Induced Electrostatic Trapping

2021-pfo-01c.jpgNanoparticle trapping in a nanofluidic device utilizing geometry-induced electrostatic (GIE) potential trap is an efficient and robust way to perform nano‑object confinement and single particle studies. The GIE‑trapping is a passive method that solely depends on the device geometry and device-particle surface interaction. Therefore, optimization of a nanofluidic device based on experimental requirements, helps to achieve stiffer single-particle trapping. The efficiency of a GIE‑trapping device is defined in terms of residence time and trapping stiffness of the nanoparticle inside a potential trap. The present study reveals all crucial parameters that affect the device efficiency, particle trapping stiffness, and particle residence time. [more...]

 

List of Publications

Structure Formation in Langmuir Peptide Films As Revealed from Coarse-Grained Molecular Dynamics Simulations
Volker Knecht, Günter Reiter, Helmut Schlaad, and Renate Reiter. Langmuir 33 (2017) 6492-6502
Schnecken als lebende 3D-Drucker: freie Formen für die Architektur von morgen
Christoph Allgaier, Benjamin Felbrich, Frederik Wulle, Emna Khechine, James H. Nebelsick, Achim Menges, Günter Reiter, Renate Reiter, Armin Lechler, Alexander Verl, Karl-Heinz Wurst. Baubionik – Biologie beflügelt Architektur, Publisher: Naturkundemuseum Stuttgart 2017
Signatures of Melting and Recrystallization of a Bulky Substituted Poly(thiophene) Identified by Optical Spectroscopy
Fanuel Keheze, Dominic Raithel, Tianyu Wu, Daniel Schiefer, Michael Sommer, Richard Hildner, Günter Reiter. Macromolecules 50 (2017) 6829–6839
Triple-Shape Memory Materials via Thermoresponsive Behavior of Nanocrystalline Non-Isocyanate Polyhydroxyurethanes
Vitalij Schimpf, Barbara Heck, Günter Reiter, Rolf Mülhaupt. Macromolecules 50 (2017) 3598–3606
Semicrystalline long-chain polyphosphoesters from polyesterification
Hanna Busch, Sumit Majumder, Guenter Reiter, Stefan Mecking. Macromolecules 50 (2017) 2706–2713
Blocking of injected holes at the charge extracting interface
L. Govor, G. Reiter, J. Parisi. Journal of Physics, Condensed Matter 29 (2017) 025001
Relaxing Non-equilibrated Polymers in Thin Films at Temperatures Slightly Above the Glass Transition
Mithun Chowdhury, Samer Al Akhrass, Falko Ziebert, Günter Reiter. Journal of Polymer Science Part B: Polymer Physics 55 (2017) 515–523
Solvent-controlled reversible switching between adsorbed self-assembled nanoribbons and nanotubes
Asad Jamal, Irina Nyrkova, Philippe Mesini, Swann Militzer and Günter Reiter. Nanoscale 9 (2017) 3293-3303
Low Loss Optical Waveguiding in Large Single Crystals of Thiophene-Based Oligomers
Sajedeh Motamen, Christian Schörner, Dominic Raithel, Jean-Pierre Malval, Thibaut Jarrosson, Françoise Serein-Spirau, Laurent Simon, Richard Hildner, Günter Reiter. Physical Chemistry Chemical Physics 19 (2017) 15980 - 15987
Time Allowed for Equilibration Quantifies the Preparation Induced Non-equilibrium Behavior of Polymer Films
Sivasurender Chandran, Rishab Handa, Marwa Kchaou, Samer Al Akhrass, Alexander Semenov, Günter Reiter. ACS Macro Lett. 6 (2017) 1296-1300
A novel interferometric method for the study of the viscoelastic properties of ultra-thin polymer films determined from nanobubble inflation
P. Chapuis , P. C. Montgomery, F. Anstotz, A. Leong-Hoï, C. Gauthier, J. Baschnagel, G. Reiter, G. B. McKenna, and A. Rubin. Review of Scientific Instruments 88 (2017) 093901
Controlling Polymer Crystallization Kinetics by Sample History
Purushottam Poudel, Sivasurender Chandran, Sumit Majumder and Günter Reiter. Macromol. Chem. Phys. 2017, 1700315
Morphological Changes of Isotactic Polypropylene Crystals Grown in Thin Films
Bin Zhang, Jiajia Chen, Baochen Liu, Binghua Wang, Changyu Shen, Renate Reiter, Jingbo Chen, Günter Reiter. Macromolecules 50 (2017) 6210−6217
Soft electrostatic trapping in nanofluidics
Michael A. Gerspach, Nassir Mojarad, Deepika Sharma, Thomas Pfohl, and Yasin Ekinci. Microsystems & Nanoengineering (2017) 3, 17051
Live cell X-ray imaging of autophagic vacuoles formation and chromatin dynamics in fission yeast
N. Strelnikova, N. Sauter, M. Guizar-Sicairos, M. Göllner, A. Diaz, P. Delivani, M. Chacon, I. M. Tolić, V. Zaburdaev, T. Pfohl, Scientific Reports 7 (2017) 13775
Second messenger-mediated tactile response by a bacterial rotary motor
I. Hug, S. Deshpande, K. S. Sprecher, T. Pfohl, U. Jenal, Science 358 (2017) 531-534
Manipulating the dewetting dynamics of polymer films by creating non-equilibrium conformational states at the interface
Adrian Linn, Master Thesis 2017
Induziertes gerichtetes Kristallwachstum einer kristallisierbaren Polymerkomponente innerhalb eines nicht-kristallisierbaren Polymernetzwerks und Untersuchung der resultierenden mechanischen Energie
Stephan Laule. Inauguraldissertation 2017
Self-Assembly and Polymerization of Diacetylene Molecules on Epitaxial Graphene
Fallou Fall, Inaugural-Dissertation zur Erlangung des Doktorgrads der Fakultät für Mathematik und Physik der Universität Freiburg, 2017
Vesicle Origami and the Influence of Cholesterol on Lipid Packing
Radu Tanasescu, Martin A. Lanz, Dennis Mueller, Stephanie Tassler, Takashi Ishikawa, Renate Reiter, Gerald Brezesinski, and Andreas Zumbuehl. Langmuir 32 (2016) 4896−4903
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