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London dispersion forces and steric effects within nanocomposites tune interaction energies and chain conformation

Baode Zhang, Snežana D. Zarić, Sonja S. Zrilić, Iosif Gofman, Barbara Heck, Günter Reiter. Communications Chemistry 8 (2025) 21

baode.jpgThe interplay between attractive London dispersion forces and steric effects due to repulsive forces resulting from the Pauli principle often determines the geometry and stability of nanostructures. Aromatic polyimides (PI) and carbon nanotubes (CNT) were chosen as building blocks as two components in the hetero delocalized electron nanostructures. Two PIs, having the same diamine part and different linkage substituents between two phenyl rings of dianhydride part, one linked with ether bond (C-O-C) (OPI), the other with C-(CF3)2 (FPI), were investigated. Surprisingly, two CNT/PI nanocomposites show distinct failure mode from CNT yielding to CNT pull-out failure. Calculation of the interaction energy and chain conformations of each PI upon CNT was performed by accurate density functional theory (DFT) calculations and molecular dynamic simulation (MDS). (more...)


Effect of chemical structure on the crystallization kinetics of triple polymorphic high-sulfur-content polythioethers

Valentina Pirela, Leire Unanue, Justine Elgoyhen, Javier Ramos, Juan Francisco Vega, Agurtzane Mugica, Manuela Zubitur, Cuong Minh Quoc Le, Abraham Chemtob, Radmila Tomovska, Günter Reiter, Jaime Martín, Alejandro J. Müller. European Polymer Journal (2025) 113721

This work studies how the chemical structure of relatively similar high-sulfur alternating polythioether homopolymers (DMDS-alt-DVE, DMDS-alt-TEGDVE, and DMDS-alt-BDDVE) affects their structural properties, morphology, polymorphism, and crystallization kinetics. Differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM) experiments revealed a complex crystallization for the samples in which up to three different polymorphic phases were identified: a very low melting crystal form (VL-Tm form), a low melting crystal form (L-Tm form) and a high melting crystal form (H-Tm form), characterized by their corresponding melting temperature ranges and confirmed via Wide-Angle X-ray Scattering (WAXS). A coexistence of negative and positive spherulites was found, and their origin was revealed by atomic force microscopy (AFM), which showed how the lamellar arrangement varied in the samples from predominantly radial to a cross-hatched morphology. (more...)
 


Post-spin Stretch Improves Mechanical Properties, Reduces Necking, and Reverts Effects of Aging in Biomimetic Artificial Spider Silk Fibers

Gabriele Greco, Benjamin Schmuck, Fredrik G. Bäcklund, Günter Reiter and Anna Rising. ACS Appl. Polym. Mater.  6 (2024) 14342–14350

reiter-2024-05.jpgRecent biotechnological advancements in protein production and development of biomimetic spinning procedures make artificial spider silk a promising alternative to petroleum-based fibers. To enhance the competitiveness of artificial silk in terms of mechanical properties, refining the spinning techniques is imperative. One potential strategy involves the integration of post-spin stretching, known to improve fiber strength and stiffness while potentially offering additional advantages. Here, we demonstrate that post-spin stretching not only enhances the mechanical properties of artificial silk fibers but also restores a higher and more uniform alignment of the protein chains, leading to a higher fiber toughness. (more...)


Mechanistically Different Mechanochromophores Enable Calibration and Validation of Molecular Forces in Glassy Polymers and Elastomeric Networks

Raphael Hertel, Maximilian Raisch, Michael Walter, Günter Reiter, Michael Sommer. Angew. Chem. Int. Ed. 2024, e202409369

sommer.jpgSterically distorted donor-acceptor p‑systems, termed DA springs, can be progressively planarized under mechanical load causing a bathochromic shift of the photoluminescence (PL) spectrum. By combining theory and experiment, we here use a simple linear force calibration for two different conformational mechanochromophores to determine molecular forces in polymers from the mechanochromic shift in PL wavelength during multiple uniaxial tensile tests. Two systems are used, i) a highly entangled linear glassy polyphenylene and ii) a covalent elastomeric polydimethylsiloxane network. The mean forces estimated by this method are validated using known threshold forces for the mechanochemical ring-opening reactions of two different spiropyran force probes. The agreement between both approaches underlines that these DA springs provide the unique opportunity for the online monitoring of local molecular forces present in diverse polymer matrices.(more...)


 

Liste der Veröffentlichungen

Tunneling of charge carriers across a gold–squaraine interface
L.V. Govor, G. Reiter and J. Parisi, Physics Letters A 380 (2016) 1493–1498
Intrinsic Stresses in Thin Glassy Polymer Films Revealed by Crack Formation
Mithun Chowdhury, Xiaoyuan Sheng, Falko Ziebert, Arnold C.-M. Yang, Alessandro Sepe, Ullrich Steiner, and Günter Reiter. Macromolecules 49 (2016) 9060−9067
Revealing Order and Disorder in Films and Single Crystals of a Thiophene-Based Oligomer by Optical Spectroscopy
Sajedeh Motamen, Dominic Raithel, Richard Hildner, Khosrow Rahimi, Thibaut Jarrosson, Françoise Serein-Spirau, Laurent Simon, and Günter Reiter. ACS Photonics 3 (2016) 2315–2323
Poly(2,5-dioctylphenyl-3-thiophene) synthesized by direct arylation polycondensation: End groups, defects and crystallinity
Daniel Schiefer, Hartmut Komber, Fanuel Mugwanga Keheze, Susanna Kunz, Ralf Hanselmann, Guenter Reiter, Michael Sommer. Macromolecules 49 (2016) 7230-7237
Transient cooperative processes in dewetting polymer melts
Sivasurender Chandran, Günter Reiter, PRL 116 (2016) 088301
Crystallization and Resulting Optical Properties of Thiophene-Based Oligomers
Sajedeh Motamen. Inaugural-Dissertation zur Erlangung des Doktorgrads der Fakultät für Mathematik und Physik der Universität Freiburg, 2016
Large area crystal surfaces of precisely sidebranched polyethylenes: Preparation, surface order and functionalization
Rainhard Machatschek. Inaugural-Dissertation zur Erlangung des Doktorgrades der Fakultät für Chemie und Pharmazie der Albert-Ludwigs-Universität Freiburg im Breisgau, 2016
Probing the Elasticity of Langmuir Polymer Films of High Molecular Weight Poly (γ-benzyl-L-glutamate)
Emna Khechine. Master Thesis im Studiengang M.Sc. Sustainable Materials, 2016
Self-assembled nanotubes and nanoribbons of aromatic diamide-esters
Asad Jamal. Inaugural-Dissertation zur Erlangung des Doktorgrads der Fakultät für Mathematik und Physik der Universität Freiburg, 2016
Formation and Optical Characterization of Single Crystals of Poly(3-Hexylthiophene) (P3HT), a Model Conjugated Polymer
John O. Agumba. Inaugural-Dissertation zur Erlangung des Doktorgrads der Fakultät für Mathematik und Physik der Universität Freiburg, 2016
History Dependent Temporal Changes of Properties of Thin Polymer Films
Günter Reiter. In: Non-equilibrium Phenomena in Confined Soft Matter. Ed. Simone Napolitano. Springer 2015
Consequences of a Single Double Bond within a Side-Group on the Ordering of Supra-Molecular Polymers
Roozbeh Shokri, Olga Guskova, Asad Jamal, Kaiwan Jahanshahi, Benjamin Isare, Laurent Bouteiller, Laurent Simon, Jens-Uwe Sommer, Günter Reiter. The Journal of Physical Chemistry, Part C 119 (2015) 22596–22603
Different surface sensing of the cell body and nucleus in healthy primary cells and in a cancerous cell line on nanogrooves
Patricia Davidson, Maxence Bigerelle, Günter Reiter and Karine Anselm. Biointerphases 10, 031004 (2015) / DOI: 10.1116/1.4927556
How Chain-Folding Crystal Growth Determines Thermodynamic Stability of Polymer Crystals
Xiaoming Jiang, Günter Reiter, Wenbing Hu. J. Phys. Chem. B, 120 (2016) 566–571
Stabilization of nuclei of lamellar polymer crystals: Insights from a comparison of the Hoffman-Weeks line with the crystallization line
Jun Xu, Barbara Heck, Hai-Mu Ye, Jing Jiang, Yi-Ren Tang, Jin Liu, Bao-Hua Guo, Renate Reiter, Dongshan Zhou, Günter Reiter. Macromolecules 49 (2016) 2206–2215
Role of Preparation Pathways and Tacticity on the Non-Equilibrium Dynamcis of Polystyrene Films
Rishab Handa. Master Thesis im Studiengang M.Sc. Sustainable Materials, 2016
Variation of the contact resistance with electric current for gold electrodes on a squaraine single crystal
Leonid Govor, Guenter Reiter, and Jurgen Parisi. Phys. Status Solidi A 212 (2015) 2738–2746, DOI 10.1002/pssa.201532241
Simulation of secondary nucleation of polymer crystallization via a model of microscopic kinetics
Kun-Lun Xu, Bao-Hua Guo, Renate Reiter, Günter Reiter, Jun Xu. Chinese Chemical Letters 26, 1105–1108 (2015) / DOI: 10.1016/j.cclet.2015.06.002
From holes to drops to toroids: Conditions for the transcription of surface patterns into three-dimensional morphologies via rim instabilities in the course of dewetting
Samer Al Akhrass, Laurent Vonna and Günter Reiter. In: Polymer Surfaces in Motion: Unconventional Patterning Methods, Eds. Juan Rodriguez-Hernandez and Carlos Drummond. Springer 2015
Tuning Morphologies of Langmuir Polymer Films Through Controlled Relaxations of Non-Equilibrium States
Sivasurender Chandran, Stefanie Dold, Amaury Buvignier, Kai-Steffen Krannig, Helmut Schlaad, Günter Reiter, and Renate Reiter. Langmuir 2015, 31, 6426−6435. DOI: 10.1021/acs.langmuir.5b01212
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