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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

The memorizing capacity of polymers
Günter Reiter. J. Chem. Phys. 152, 150901 (2020)
Formation of asymmetric leaf-shaped crystals in ultrathin films of oriented polyethylene molecules resulting from high-temperature relaxation and recrystallization
Huihui Li, Duanzijing Liu, Xinyun Bu, Zhenzhen Zhou, Zhongjie Ren, Xiaoli Sun, Renate Reiter, Shouke Yan, Günter Reiter. Macromolecules 53 (2020) 346-354
Controlling phase transitions in Langmuir polymer films
Abhijna Das. Inauguraldissertation der Fakultät für Mathematik und Physik 2020. DOI: 10.6094/UNIFR/167266
Controlling Nucleation in Quasi-Two-Dimensional Langmuir Poly(L-lactide) Films through Variation of the Rate of Compression
Abhijna Das, Ahmed S. El-Tawargy, Emna Khechine, Sebastian Noack, Helmut Schlaad, Günter Reiter, and Renate Reiter. Langmuir 35 (2019) 6129-6136
Activity of the Gramicidin A Ion Channel in a Lipid Membrane with Switchable Physical Properties
Renate Reiter, Ekaterina Zaitseva, Gerhard Baaken, Ibrahim Halimeh, Jan C. Behrends, Andreas Zumbuehl. Langmuir 35 (2019) 14959-14966
Dewetting Rheology for Determining Viscoelastic Properties of Non-equilibrated Thin Polymer Films
Austine A. Mulama, Sivasurender Chandran, Konstantinos Roumpos, Andrew O. Oduor, and Günter Reiter. Macromolecules 52 (2019) 7894-7903
Relation between Charge Transport and the Number of Interconnected Lamellar Poly(3-hexylthiophene) Crystals
Binghua Wang, Jingbo Chen, Changyu Shen, Günter Reiter, Bin Zhang. Macromolecules 52 (2019) 6088-6096
Fully Isotactic Poly(p-methylstyrene): Precise Synthesis via Catalytic Polymerization and Crystallization Studies
Tianyu Wu, Luis Valencia, Thomas Pfohl, Barbara Heck, Günter Reiter, Pierre Lutz, Rolf Mülhaupt. Macromolecules 52 (2019) 4839-4846
Photoelectronic properties of composite films based on conductive polymer PIDT-BT and single-walled carbon nanotubes
Andrey N. Aleshin, Baode Zhang, Petr A. Aleshin, Vasily N. Petrov, Irina N. Trapeznikova, Günter Reiter, Janis Kleperis. SN Applied Sciences 1 (2019) 1101
Segmental Rearrangements Relax Stresses in Nonequilibrated Polymer Films
Sivasurender Chandran, Günter Reiter. ACS Macro Letters, 8, 646, (2019)
Thermodynamic Features of Perfectly Crystalline Poly(3-Hexylthiophene) Based on Flory’s Relation
Mina Alizadehaghdam, Silvia Siegenführ, Farhang Abbasi, and Günter Reiter. Journal of Polymer Science Part B: Polymer Physics 57, 431–437 (2019)
Thermodynamic Features of Perfectly Crystalline Poly(3-hexylthiophene) Revealed Through Studies of Imperfect Crystals
Mina Alizadehaghdam, Barbara Heck, Silvia Siegenführ, Farhang Abbasi, and Günter Reiter. Macromolecules 52 (2019) 2487–2494
A Structural Fibrillation Parameter from Small Angle X-ray Scattering to Quantify Pulp Refining
Jia Mao, Barbara Heck, Hatem Abushammala, Günter Reiter, and Marie-Pierre Laborie. Cellulose 26 (2019) 4265–4277
Following isothermal and non-isothermal crystallization of poly(3- hexylthiophene) thin films by UV-vis spectroscopy
Mina Alizadehaghdam, Barbara Heck, Silvia Siegenführ, Yaser AlShetwi, Fanuel M. Keheze, Sebastian Stäter, Farhang Abbasia, Günter Reiter. Polymer 210 (2020) 122959
Snails as living 3D printers: free forms for the architecture of tomorrow
Christoph Allgaier, Benjamin Felbrich, Frederik Wulle, Emna Khechine, James H. Nebelsick, Achim Menges, Günter Reiter, Renate Reiter, Armin Lechler, Alexander Verl, Karl-Heinz Wurst. In Knippers, J; Schmid, U.; Speck, T. (eds.) Biomimetics for Architecture, Birkhäuser, Basel 2019, pp 126-133. (ISBN: 978-3-0356-1791-7)
Controlling the Growth of Stacks of Correlated Lamellar Crystals of a Block Copolymer
Sumit Majumder, Renate Reiter, Jun Xu and Günter Reiter. Macromolecules 52 (2019) 9665-9671
Determination of the Critical Size of Secondary Nuclei on the Lateral Growth Front of Lamellar Polymer Crystals
Shujing Zhang, Jiarui Han, Yang Gao, Bao-Hua Guo, Günter Reiter, Jun Xu. Macromolecules 52 (2019) 7439-7447
A Nucleation Mechanism Leading to Stacking of Lamellar Crystals in Polymer Thin Films
Sumit Majumder, Purushottam Poudel, Hui Zhang, Jun Xu, Günter Reiter. Polymer International 69 (2020) 1058
Processing Pathways Decide Polymer Properties at the Molecular Level
S. Chandran, J. Baschnagel, D. Cangialosi, K. Fukao, E. Glynos, L. M. C. Janssen, M. Müller, M. Muthukumar, U. Steiner, J. Xu, S. Napolitano, and G. Reiter. Macromolecules 52 (2019) 7146-7156
Controlling the Pore Size in Conjugated Polymer Films via Crystallization-Driven Phase Separation
Shaowen Guo, Changyu Shen, Jingbo Chen, Günter Reiter, Bin Zhang. Soft Matter 15 (2019) 2981-2989
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