Martin Luther University Halle-Wittenberg

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Institut für Physik - NMR

phone: +49 (0) 345 55 28551

Betty-Heimann-Str. 7
06120 Halle (Saale)

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Upcoming P3S Webinars

The online meetings take place via Zoom [click here] and open at about 1:40 pm UTC for testing and informal chat among the participants (meeting ID: 876 8664 6314, password: 459406).

Thursday, November 12, 2020, 3 pm CET

Prof. Dr. Wenke Zhang

State Key Lab of Supramolecular Structure and Materials, Jiling U, Changchun

Single-molecule study on the molecular interactions and folding mode in polymer single crystals

Abstract:
Establishing the relationship between the molecular structure and nanomechanical properties in lamellar crystals is of fundamental importance for the development of advanced crystalline polymer materials. We have used atomic force microscopy (AFM)-based single-molecule force spectroscopy and steered molecular dynamic simulations to investigate molecular interactions as well as the folding mode of a polymer chain within the single crystal at single-molecule level. Effects of chain conformation/composition, crystal thickness and environment on molecular interactions and dynamic force-induced melting process were studied.

Prof. Dr. Thomas Thurn-Albrecht

Inst. of Physics, Martin-Luther-Univ. Halle-Wittenberg

How intracrystalline chain dynamics determines the the morphology of semicrystalline polymers

Abstract:

The characteristic morphological feature of semicrystalline polymers is a nanoscopic non-equilibrium structure of thin lamellar crystals separated by amorphous layers. Which kinetic or thermodynamic factors control the crystal thickness is an old but still debated question in polymer physics. Using a combination of NMR and SAXS we show how this morphology results from a competition between crystal growth and reorganization by intracrystalline chain dynamics.

Thursday, November 26, 2020, 3 pm CET

Dr. Oleksandr Dolynchuk

Inst. of Physics, Martin-Luther-Univ. Halle-Wittenberg

Thermodynamic foundations of crystallization via prefreezing: the case of no nucleation

Abstract:
Crystallization of liquids is usually initiated at the interface to a  solid. The underlying process can be either heterogeneous nucleation or  the less known process of prefreezing. In my talk, I will present the  recent theoretical and experimental results on thermodynamics of  prefreezing with a special focus on the substrate influence.

Prof. Dr. Toshikazu Miyoshi

School of Polymer Science and Polymer Engineering, U Akron

Molecular Dynamics, Phase Transition, and Structural  Evolution in Configurationally and Conformationally Disordered Polymer Crystals

Abstract:
Fast  and anisotropic chain dynamics coupled with structural disorder  significantly contribute to structural evolution of several  semicrystalline polymers. We report a new class of structural disorder,  “configurational disorder coupled with conformational flexibility  (CDCF)” in polymer crystals. It is revealed that atactic-hydrogenated  poly(norbornene) (hPNB) conducts slow conformational dynamics below crystal-crystal transition temperature (Tcc) and fast uniaxial chain dynamics above Tcc while isotactic (i)- and syndiotactic (s)-hPNBs do not perform such fast chain dynamics. It is for the first time demonstrated that the presence of fast chain dynamics leads to much higher crystallinity (80 %) and much longer long-period (L = 96 nm) in a-hPNB than those of s- and i-hPNBs (crystallinity of 50-55 % and L of 17-21 nm). It is concluded that CDCF plays an important role for phase transitions, fast chain dynamics, and unique structural evolution in stereo-irregular polymers.

Thursday, December 10, 2020, 3 pm CET

Dr. Yang Yao

Laboratory of Food and Soft Materials, ETH Zürich

Crystallization and dynamics of polymer and water under nano-sized confinement

Abstract:
Polymer topology has inevitable influence on the structure, packing, and dynamic of chains. I will present the impact of polymer architecture on crystallization under 2D confinement of nanoporous alumina. In contrast to the heterogeneous nucleation in the bulk, mainly homogeneous nucleation is observed under confinement. The homogeneous nucleation temperature of the non-linear topologies is identical to that of linear ones, provided that the arm, branched, or the block molecular weight is used instead of the total molecular weight. In addition, the segmental dynamics speeds-up reflecting a reduction in glass temperature. Furthermore, I will present crystallization and dynamics of confined water. Many biological processes take place in crowded aqueous surroundings and water in living cells can be considered as confined water, which behaves differently with respect to the nucleation mechanism and the molecular dynamics comparing to the bulk. Building on first results on water nano-confined to silica, the talk will present cutting edge results on water in biomimetic environment, which will shed light on the understanding of life in extreme environment.

Prof. Dr. Ernst Rössler

Experimental Physics, Universität Bayreuth

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Thursday, January 7 or 21, 2021, 3 pm CET

Prof. Dr. Robert Hickey

Materials Science and Engineering, Penn State U

Solvent-Non-Solvent Rapid Injection for the Preparation of Hierarchically Ordered Hydrogels

Abstract:
Recent  work has shown that non-solvent-induced phase separation methods will  produce hierarchically ordered physically crosslinked hydrogels when  using amphiphilic triblock copolymers  comprising of a hydrophobic-hydrophilic-hydrophobic chain sequence. The  polymers, initially in a water miscible good solvent, will rapidly  self-assemble at the nano and microscale when injected into water. The  presentation will cover the rapid-injection method  to produce physically crosslinked hydrogels, and the impact of the  processing conditions on the mechanical properties and hierarchical  structure of the hydrogels.

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