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Recent Publications


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 Applied Polymer Materials, published online

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...)


"Printing" on Polymer Single Crystals through Microregional Heating

Tianyu Wu, Haimu Ye, Xinyi Pan, Yaning He, Jun Xu, Günter Reiter. ACS Appl. Polym. Mater. 2024, 6, 14, 7969–7977

tianyu.jpgPolymer single crystals are composed of well-ordered polymer chains and possess a characteristic symmetric shape. If one can precisely control the microregional morphology, polymer single crystals have the potential to be used as functional templates for applications like information storage or cell culture. However, with current experimental approaches, it is rather difficult to generate predictable structures of defined size within polymer single crystals. Here, we propose a research strategy based on a combination of fluorescence labeling and microregional heating by irradiation with focused red light. This approach enabled us to locally heat single crystals while simultaneously following the thereby induced changes via fluorescence imaging with a micrometer lateral resolution. We found that polymers diffused out of the heated region within a stacked single crystal and thereby produced a hole at the irradiated location. (more...)


Mechanism for the Formation of Millimeter-Long Solid Filaments by Spin Coating Dilute Solutions of a Crystallizable Polymer

Da Huang, Thorsten Hugel, and Günter Reiter. Macromolecules 2024, 57, 3696–3705

huang.jpgWe have investigated the formation of millimeter-long filaments induced by spin-coating ca. 130 °C dilute para-xylene solutions of rapidly crystallizable polyethylene chains with a contour length in the micrometer range onto ca. 80 °C mica substrates. These filaments were radially oriented and accumulated on the periphery of the substrate. Our observations can be explained by the stretching of polymers through the flow field induced by spinning the solution on a solid substrate. The corresponding loss in conformational entropy emphasized attractive interactions between polymers, which resulted in the formation of bundles and their assembly into long filaments. Caused by a Plateau–Rayleigh-type instability of a liquid coating on a solid filament and due to crystallization, these filaments were decorated with various small-scale structures. (more...

 

List of Publications

The effect of molecular association and tube dilation on the rotational viscosity and rotational diffusion in nematic liquid crystals
A. Raviol, W. Stille, and G. Strobl. J. Chem. Phys. 103, 3788 (1995)
Nematic Wetting at the Free-Surface of 4-Cyano-4'-N-Alkyl-Biphenyls
H. Kasten, G. Strobl. Journal of Chemical Physics 103, 6768-6774 (1995)
The Dynamics of Freedericksz Transitions in Nematic Solutions of Mesogenic Polymers
E. E. Pashkovsky, T. G. Litvina, W. Stille, and G. Strobl. Vysokomolekulyarnye Soedineniya Seriya A 37, 1272 (1995)
Self Diffusion of “Hairy Rod” Molecules in Langmuir-Blodgett-Kuhn Multilayers Probed with Neutron and X-ray Reflectometry
A. Schmidt, K. Mathauer, G. Reiter, M.D. Foster, M. Stamm, G. Wegner, W. Knoll. Langmuir 10, 3820 (1994)
Stick to Slip Transition and Adhesion of Lubricated Surfaces in Moving Contact
G. Reiter, A.L. Demirel, J. Peanasky, L. Cai, S. Granick. J. Chem. Phys. 101, 2606 (1994)
From Static to Kinetic Friction in Confined Liquid Films
G. Reiter, A.L. Demirel, S. Granick. Science 263, 1741 (1994)
Dewetting as a Probe of Polymer Mobility in Thin Films
G. Reiter. Macromolecules 27, 3046 (1994)
Chain Reorientation in Poly(tetrafluoroethylene) by Mobile Twin-Helix Reversal Defects
M. Kimmig, G. Strobl, B. Stühn. Macromolecules 27, 2481-2495 (1994)
Local Motion in the beta-Transition Range of Partially Crystalline Polyethylene Studied by Neutron-Scattering
B. Holzer, G. Strobl, B. Stühn, N.H. Andersen. Colloid and Polymer Science 272, 1396-1402 (1994)
Dynamics of Rotational Motion in Liquid Crystalline Systems
W. Stille, G. Strobl. in: R. Richert, A. Blumen (Eds.), Disorder Effects on Relaxational Processes, p. 725, Springer, Berlin (1994).
Molecular Weight Dependence of the Rotational Diffusion Constant and the Rotational Viscosity of Liquid Crystalline Side Group Polymers
S. Götz, W. Stille, G. Strobl, H. Scheuermann. Macromolecules 26, 1520 (1993)
Near-Critical Behavior of the Dynamic Stress-Optical Coefficient in Liquid Crystalline Elastomers
R. Sigel, W. Stille, G. Strobl and R. Lehnert. Macromolecules 26, 4226 (1993)
Adhesion Instabilities of Surfaces Undergoing Shear
G. Reiter, J.S. Peanasky, L. Cai, A.L. Demirel, S. Granick. ACS Polymer Preprint Fall 1993
Dynamics of Polymer Interdiffusion at Short Times
U. Steiner, G. Reiter. Proceedings of the Les Houches Conference 1991: Dynamical Phenomena at Interfaces, Surfaces and Membranes, D. Beysens, N. Boccara, G. Forgacs, eds., Nova Science Publishers, New York, p. 511-512 (1993)
Unstable Thin Polymer Films: Rupture and Dewetting Processes
G. Reiter. Langmuir 9, 1344 (1993)
Mobility of Polymers in Films Thinner Than Their Unperturbed Size
G. Reiter. Europhysics Letters 23, 579 (1993)
Investigation of the Interdiffusion between Poly(methylmethacrylate) Films by Marker Movement
Y. Liu, G. Reiter, K. Kunz, M. Stamm. Macromolecules 26, 2134 (1993)
Short Time Dynamics of Polymer Diffusion
G. Reiter, U. Steiner. Progr. Colloid and Polymer Science 91, 93 (1993)
Transition Regions and Surface Melting in Partially Crystalline Polyethylene: A Raman Spectroscopic Study
R. Mutter, W. Stille, and G. Strobl. J. Polym. Sci. Part B: Polym. Phys. 31, 99 (1993)
Smectic Surface-Structures in the Isotropic-Phase of Liquid-Crystalline Polymers Studied by X-Ray Reflectivity
H. Elben, G. Strobl. Macromolecules 26, 1013-1018 (1993)
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