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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

Thin Film Instability Induced by Long Range Forces
G. Reiter, A. Sharma, A. Casoli, M.O. David, R. Khanna, P. Auroy. Langmuir 15, 2551-2558 (1999)
Network stretching, slip processes, and fragmentation of crystallites during uniaxial drawing of polyethylene and related copolymers. A comparative study
R. Hiss, S. Hobeika, C. Lynn, G. Strobl. Macromolecules 32, 4390-4403 (1999)
Reversible surface melting of PE and PEO crystallites indicated by TMDSC
W.B. Hu, T. Albrecht, G. Strobl. Macromolecules 32, 7548-7554 (1999)
A general scheme derived from video-controlled stretching tests and WAXS for describing tensile deformations of polyethylenes
R. Hiss, S. Hobeika, C. Lynn, G. Strobl. Journal of Macromolecular Science - Physics B38, 847-858 (1999)
Steps in the transition of an entangled polymer melt to the partially crystalline state
B. Heck, T. Hugel, M. Iijima, E. Sadiku, G. Strobl. New Journal of Physics 1, 17 (1999).
Building lamellae from blocks: The pathway followed in the formation of crystallites of syndiotactic polypropylene
T. Hugel, G. Strobl, R. Thomann. Acta Polymerica, 50, 214 (1999)
Adhesion Failure and Dewetting of Thin Liquid Films
A. Sharma, R. Khanna and G. Reiter. Festschrift on Adhesion Science and Technology, p. 199-237, W.J. van Ooij and H.R. Anderson, eds., VSP Publishers, Utrecht (1998)
Détermination de forces intermoléculaires par microscopie optique: effet de connecteurs polymères
A.Casoli, G.Reiter, M.Brendlé, J. Schultz. Ouvrage des actes “Imagerie des Polymères” (Colloque international francophone, Nancy, Février 1998, (Apollor)
Self-assembly of Crystallisable Diblock Copolymers
G. Reiter, P. Hoerner, G. Hurtrez, G. Riess, J.-U. Sommer, J.-F. Joanny. J. Surf. Sci. Tech. 14 , 93-103 (1998)
Role of Intermolecular Interactions in Pattern Formation in Unstable Thin Films
A. Sharma, G. Reiter. Metals Materials and Processes 10, 287-302 (1998)
The artistic side of intermolecular forces
G. Reiter. Science 282, 888-889 (1998)
Structure and dynamics of structure formation in model triarm star block copolymers of polystyrene, poly(ethylene oxide), and poly(epsilon-caprolactone)
G. Floudas, G. Reiter, O. Lambert, P. Dumas. Macromolecules 31, 7279-7290 (1998)
Crystallisation of Adsorbed Polymer Monolayers
G. Reiter, J.-U. Sommer. Phys. Rev. Lett. 80, 3771 (1998)
Deformation of a Glassy Polymer Film by Long-Range Intermolecular Forces
M.O. David, G. Reiter, T. Sitthai, J. Schultz. Langmuir 14, 5667-5672 (1998)
Capillary waves on a poly(vinylacetate) surface studied by off-specular diffuse X-ray scattering
S. Bauer, G.R. Strobl. Polymer Bulletin 40, 291-296 (1998)
Superheating effects during the melting of crystallites of syndiotactic polypropylene analysed by temperature-modulated differential scanning calorimetry
J.E.K. Schawe, G.R. Strobl. Polymer 39, 3745-3751 (1998)
The role of co-units in polymer crystallization and melting: New insights from studies on syndiotactic poly(propene-co-octene)
G. Hauser, J. Schmidtke, G. Strobl. Macromolecules 31, 6250-6258 (1998)
Synthesis and microphase separation of diblock copolymers of styrene and p-chlorostyrene prepared by using N-oxyl capped macroinitiators
S. Butz, J. Hillermann, G. Schmidt-Naake, J. Kressler, R. Thomann, B. Heck, B. Stühn. Acta Polymerica 49, 693-699 (1998)
La réflectivité des polymères
G. Reiter. Chapitre VIII dans les actes de l'ecole française de réflectivité, à Marseille 1997, Eds. A. Gibaud, J. Daillant
Surfactants: Eigenschaften und Einsatz in der Beschichtungstechnik
G. Reiter. Kapitel 5: in Grundlagen und Verfahren der Beschichtungstechnik, Kurzlehrgang, Erlangen 1997
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