Thursday, June 11, 2020, 4 pm CEST

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Prof. Dr. Enrique D. Gomez

Dept. of Chemical Engineering, Penn State University, University Park, PA, USA

Local Chain Alignment Via Nematic Ordering Reduces Chain Entanglement in Conjugated Polymers

Abstract:
Conjugated polymers provide an opportunity to examine the role of  entanglement in melts of semiflexible polymers.  Given that liquid  crystallinity is ubiquitous in this class of materials, we examined the  role of nematic order on entanglement in a few model systems. The onset  of local chain alignment reduces entanglement, resulting in an order of  magnitude increase in the entanglement length.

Dr. Ryan C. Nieuwendaal

Materials Science and Engineering Division, NIST, Gaithersburg, MD, USA

An examination of OPV interfacial structures from REDOR NMR data and analysis

Abstract:
Structures in mixed amorphous phases control important OPV properties such fill factor and donor/acceptor interfacial area. Unfortunately, these regions are both difficult to measure because of their fine size scales and irregular packing patterns, and difficult to predict because there are numerous parameters that control the kinetics and thermodynamics of BHJ film formation. In this talk, I will give highlights of ¹³C-²H REDOR solid-state NMR measurements on a P3HT-PCBM BHJ film, and show that when paired with molecular dynamics simulations, important interfacial characteristics can be unveiled. Although, the structures that result from pairing solid-state NMR and MD simulations are not unique, we show that the donor/acceptor interfacial characteristics can be well-defined, which will be important for future work in predicting structures in mixed amorphous phases in general.

Thursday, June 25, 2020, 4 pm CEST

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Prof. Dr. Michael R. Hansen / Steffen Böckmann

Institut für Physikalische Chemie, Universität Münster, Germany

How Molecular Packing and Conformation Translates into Function in π-Conjugated Polymers Revealed by Solid-State NMR

Abstract:
Polymers with extended π-conjugation may serve as organic semiconductors in various electron devices. Their function is established via solution processing, which results in active materials that are semi crystalline with no pronounced long-range ordering. This prevents the direct access to details about molecular organization, conformation, and packing from a conventional approach. Here, two examples will be given where small molecular changes lead to subtle changes in the performance of the respective π-conjugated polymers. The changes in performance are elucidated using a combination of experimental techniques, where the decisive molecular insights are provided from a multinuclear approach via one- and two-dimensional ¹H, and ¹⁹F solid-state NMR experiments.

Prof. Dr. Yu Zhu

Dept. of Polymer Science, U Akron, OH, USA

Molecular Packing of π-Conjugated Molecules through Fused Hydrogen Bond-mediated Self-assembly

Abstract:
The molecular arrangement is pivot for charge transport in organic materials. Understanding the interplay between intermolecular interactions and crystal structure and being able to control it are essential to achieving the desired molecular packing, crystal structure and alignment/interconnection of the crystalline grains, enabling the control of charge transfer in organic materials. In this presentation, a fused hydrogen bond-mediated self-assembly was demonstrated to control the molecular packing of conjugated molecules. When hydrogen bonding sites are fused with the π-plane of the conjugated molecules, the orientations of hydrogen bonding and π-plane are directly related. Therefore, the directional characteristic of hydrogen bonding will guide the formation of π-π stacking in a specific direction, leading to the enhancement of charge transport.

Thursday, July 9, 2020, 4 pm CEST

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Prof. Dr. Karen I. Winey

Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia

Self-Assembly of Segmented Polyolefin Ionomers:  New Morphologies and Ion Conductivity

Abstract:
Controlling the self-assembled nanoscale ionic aggregates in single-ion conducting polymers is a crucial step toward exceptional transport properties. We report a series of precisely-segmented polyethylene-like ionomers containing sulfonate groups (PES) with Li+, Na+, Cs+, or NBu4+ counterions synthesized from step-growth polymerization. At room temperature, the PES ionomers with 23 or 48 methylene units are semicrystalline with well-defined nanoscale ionic layers with spacings influenced by the spacer length and cation. In situ X-ray scattering measurements reveal that the layered ionic aggregates in PES23Li, PES23Na, and PES23Cs transform, upon melting the PE segments, into the Ia3 ̅d gyroid morphology. The gyroidal ionic aggregates in PES23Li and PES23Na further evolve into hexagonal symmetry as the temperature increases. These order-to-order transitions in ionic aggregate morphologies were also confirmed by oscillatory shear rheology. The ion transport behavior of these PES23 polymers is strongly dependent on the ionic aggregate morphologies. Specifically, the 3D interconnected gyroid morphology of PES23Li exhibits higher ionic conductivity than the isotropic layered or hexagonal morphologies. This innovative and versatile molecular design of ionomers leads to unprecedented percolated gyroidal ionic aggregate morphologies that provide a continuous pathway for improved ion transport.

Prof. Dr. Yefeng Yao

Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai

Suppressing crystallinity of semicrystalline polymer electrolyte by exploiting the ion concentration difference between the phase structures

Abstract:
Solid-state polymer electrolytes (SPEs) have attracted a lot of research interests for their promising applications in all-solid-state rechargeable batteries. Comparing with the ceramic electrolytes, the virtues of semi-crystalline SPEs lie on the superior elasticity and plasticity which are very crucial for the material processibility and recycle stability of the batteries. At the present time the practical application of SPE on the battery industry is limited by the low conductivity of SPE. Reducing the crystallinity has been approved to be an effective approach to improve the conductivity of SPE. In this work, we will present a novel and general way to reduce crystallinity of SPE by exploiting the ion concentration difference between the different phase structures in SPEs. We will show that we are able to prepare a complete amorphous PEO/Li⁺ SPE. Similarly, by controlling ion concentration difference between the different phase structures we could also prepare the PEO/Li⁺ crystals containing high content of defects. In such crystals, the segmental mobility is 2 orders higher than that of the normal PEO/Li⁺ crystals. Varied NMR techniques were performed to understand the structure and dynamics in the samples. The implications of this work on developing high conductive SPE are discussed afterwards.

Thursday, July 23, 2020, 4 pm CEST

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Prof. Dr. Monika Schönhoff

Institute of Physical Chemistry, University of Münster, Germany

Electrophoretic NMR to determine ion mobilities and correlated ion transport in poly- and oligo-ethyleneoxide- based electrolytes

Abstract:

Ion transport in electrolyte materials, e.g. for Li ion batteries, is often influenced by the strong ion correlations in concentrated electrolytes. Commonly employed multinuclear (e.g. ¹H, ⁷Li, ¹⁹F) Pulsed-Field-Gradient (PFG)-NMR diffusion is not sufficient to identify the conductivity contributions of specific ion species, since the electrophoretic mobility µ has to be known. Electrophoretic NMR (eNMR) allows to directly measure the electrophoretic mobility of ions with NMR-active nuclei. The lecture focusses on its application to polymeric and oligomeric (glyme) electrolyte systems. Drift velocities of ions and even of uncharged molecular components in the electric field can be identified and lead to conclusions on Li⁺ coordination and the role of anticorrelations of different ion species.

Prof. Dr. Bryan Vogt

Dept. of Chemical Engineering, Penn State University, University Park, PA, USA

Are ionomers ideal polymers for 3D printing via material extrusion?

Abstract:
3D printing has been used to address some medical supply shortages  during the COVID-19 pandemic with thermoplastics being used to craft  components for face shields, ventilators and various other personal  protective equipment and medical  supplies worldwide. Obtaining desired fit (shape accuracy) and function  (properties) for 3D printed plastics can be challenging. Here, I will  illustrate how ionomers can be readily 3D printed and how these printed  ionomers can produce new functionality and  significant improvements in properties. Some of the limitations of  material extrusion-based can be readily addressed with ionomers due to  their structure and dynamics.

Thursday, September 3, 2020, 4 pm CEST

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Dr. Cedric Lorthioir

Laboratoire de Chimie de la Matière Condensée de Paris, Sorbonne Université, Paris

Topology and dynamical processes in polymer-based gels: An insight  from solid-state NMR

Abstract:
Continuous research efforts have been dedicated over the last decade to  design gel architectures with improved, and also tunable, mechanical  behaviors. The modeling of such properties is a non-trivial issue since  it involves both structural and dynamical descriptions related to  various length and time scales. Gel topology is one of the key  structural information that cannot be easily determined experimentally  while solid-state NMR appears as a well-suited and powerful approach to  probe both elastically active chains and defects. The gel mechanical  behavior is also influenced by dynamical processes occurring at  different length / time scales: the (global) chain dynamics on the one  hand, and the (more local) segmental motions on the other hand. Again,  solid-state NMR may provide an excellent opportunity to investigate  these motions, thus allowing correlations with the mechanical properties  to be determined. These features will be exampled and discussed through  two kinds of physical gels: hybrid (clay-based) hydrogels and ionic  organogels.

Prof. Dr. Costantino Creton

Laboratory of Soft Matter Science and Engineering, ESPCI Paris Tech

Polymer gels with permanent and dynamic bonds:  relationship between dynamics and large strain behavior and fracture.

Abstract:
In recent years there has a lot of interest in improving the resistance to fracture of hydrogels by modifying their network topology. One such toughening strategy has been to combine a population of permanent chemical crosslinks with a population of physical reconfigurable crosslinks. While the effect of dynamic crosslinks on linear rheology has been well studied, the large strain behavior and in particular the fracture behavior of the gels remains more complex and involves not only the dynamics but the change in network topology as bonds break. We will present some recent results and discuss some open questions on connecting molecular structure and fracture of gels.

Thursday, September 17, 2020, 4 pm CEST

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Prof. Dr. Alexei Sokolov

U Tennessee, Knoxville

Designing Polymer Nanocomposites: Critical Role of the Interfacial Layer

Abstract:
In this talk we overview recent studies on structure and dynamics of the interfacial layer in various polymer nanocomposites (PNCs). We employ broad array of experimental techniques and MD-simulations that provide detailed characterization of the interfacial layer. These studies revealed a gradient in the interfacial layer dynamics, but no “glassy” or “dead“  layer. The thickness of the interfacial layer increases upon cooling to Tg, and depends strongly on polymer rigidity, increasing from ~2nm in flexible polymers to ~5 nm in more rigid ones. We discuss a possible connection of the interfacial layer thickness to the dynamic heterogeneity length scale. We emphasize usually overlooked dynamic property of the interfacial layer – strong suppression of the amplitude of structural relaxation on time scale of segmental dynamics. At the end, we present a general picture how microscopic parameters control the interfacial layer, and how by tuning the interfacial layer we can tune macroscopic properties of polymer nanocomposites.  

Prof. Dr. Linda Reven

McGill U, Montreal

Liquid Crystal Polymer Nanocomposites

Abstract:
Inorganic nanoparticles and polymers are being combined  with liquid crystals to both understand the effect of these additives on  liquid crystal properties and to create new hybrid materials.This  lecture will give an overview of our past and current studies, focusing  on the role of the polymer chain flexibility in producing stable  dispersions versus controlled phase separations.

Thursday, October 1, 2020, 4 pm CEST

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Prof. Dr. Nitash Balsara

Chemical and Biomolecular Engineering, UC Berkely

Ion transport in polymer electrolytes for lithium batteries and electrophoretic NMR

Abstract:
I will discuss some of the fundamental factors that limit ion transport in polymers.  In all electrolytes, the current generated at steady state is governed by the applied potential.  This relationship, which one might call a modified Ohm’s Law, depends on Stefan-Maxwell diffusion coefficients.  We find that these diffusion coefficients in many electrolytes are negative over a substantial salt concentration range.  The relationship between Stefan-Maxwell diffusion coefficients and ion velocities measured by electrophoretic NMR will be discussed.  

Prof. Dr. Lou Madsen

Dept. of Chemistry, Virginia Tech, Blacksburg

Tracking motions in soft materials by NMR diffusometry: Discoveries and dangers

Abstract:
Our group combines NMR  transport measurements that are species-specific and length/time-scale  specific with structural and dynamical information to build  comprehensive models for the behaviors of soft materials.   I will touch on transport phenomena in polymer-based systems that  include nanometer-scale confinement in separations membranes, and drug  and chain partitioning in micelles.  I will also describe a few of the  classic (and yet still ubiquitous) pitfalls in the  interpretation of NMR diffusion data.

Thursday, October 15, 2020, 4 pm CEST

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Dr. Whitney Loo

(Chemical and Biomolecular Engineering, UC Berkely)
(U Chicago)

Polymer dynamics in block copolymer electrolytes detected by neutron spin echo spectroscopy

Abstract:
We investigated the effect of salt concentration on the  polymer dynamics of a nanostructured block copolymer electrolyte on the  0.1-100 ns time-scale using the Rouse and reptation tube model. In this  talk, I will demonstrate how quantifying chain motion in the presence of  ions is essential for predicting the behavior of  polymer-electrolyte-based batteries operating at large currents.

Prof. Dr. Michael Vogel

Dept. of Physics, Solid-State Physics, Technische Universität Darmstadt

NMR studies of rotational and translational diffusion in polymer electrolytes and ionic liquids

Abstract:
In my talk, I will combine manifold NMR methods to study rotational dynamics and translational diffusion in polymer electrolytes and ionic liquids in broad ranges of time and length scales. In particular, I will discuss to which extent nanoscopic concentration fluctuations in these mixtures affect the relation of local and diffusive dynamics for the individual constituents and, thus, the transport mechanisms.

Thursday, October 29, 2020, 3 pm CET

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Prof. Dr. Mitsushiro Shibayama

Institute for Solid State Physics, University of Tokyo

DLS Studies of Speckle-free gels and Crowed Microgels

Abstract:
Dynamic light scattering (DLS) is a powerful tool for investigations of the dynamics of complex fluid systems. Here, we report DLS studies of polymer gels and microgels, which are non-ergodic and characterized by strong speckles in light scattering originating from frozen-concentration fluctuations in the gel. It has been believed that the appearance of speckles is inherent for polymer gels. Recently, however, we developed speckle-free gels which do not show any change in both static and dynamic scattering while they undergo rheological sol-gel transition. The strategy for the preparation of speckle-free gels will be discussed. The second topic is a DLS study of microgels in a wide concentration range from dilute to concentrated across a jamming transition, achieved by using tens-nanometer sized microgels which do not scatter light. Universal/specific features of time-intensity correlation functions in complex fluid systems will be discussed.

Dr. Todd M. Alam

Dept. of Organic Material Sciences, Sandia Nat'l Laboratories, Albuquerque

Exploring High Resolution Magic Angle Spinning (HRMAS) NMR Diffusometry in Swollen Polymers and Gels

Abstract:
In this presentation I will describe our efforts in combining high resolution magic angle spinning (HRMAS) NMR spectroscopy and pulse field gradient (PFG) NMR diffusometry techniques to measure mixtures in swollen polymer materials. Magnetic susceptibility differences for liquids absorbed in heterogenous materials are significant, but MAS efficiently suppresses these differences resulting in dramatic improvements of the NMR spectral resolution, thereby allowing the use of PFG NMR diffusion experiments to probe multiple chemical environments simultaneously. I will discuss a few examples of successes in 1H HRMAS NMR diffusometry, as well as some caveats.

Thursday, November 12, 2020, 3 pm CET

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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

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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 (T_cc) and fast uniaxial chain dynamics above T_cc 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

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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

Polymer dynamics as revealed by field-cycling NMR

Abstract:
Employing commercial and home-built field-cycling (FC) relaxometers we measure the dispersion of spin-lattice relaxation rate. Assuming frequency-temperature superposition master curves extending over many decades in amplitude  and frequency are constructed from relaxation spectra taken in a broad temperature range. In the case of protons,  due to the intra- and intermolecular origin of dipolar interactions,  relaxation dispersion  reflects rotational as well as translational dynamics. The latter  displays a universal low frequency dispersion law which allows  determining the diffusion coefficient in addition to the segmental time  constant. Sub-diffusive  translation typical of polymers is accessed by singling out the  intermolecular  relaxation via isotope dilution experiments. Thereby, the mean square  displacement is accessed, complementing neutron scattering experiments.  Likewise, information on segmental reorientational dynamics is provided  by the intramolecular relaxation. All in all,  thorough testing of current polymer theories becomes possible, and FC  NMR will prove itself as a method of molecular rheology.

Thursday, January 7, 2021, 3 pm CET

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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.

Prof. Dr. Patrick C. A. van der Wel

Zernike Institute for Advanced Materials, U Groningen

Solid-state NMR of repetitive biopolymer hydrogels: tackling polyglutamine proteins and polysaccharide hydrogels

Abstract:
Hydrogels are of interest in both biology and materials science, but often hard to study in detail. We study by solid-state NMR several hydrogel-forming biopolymers with repetitive chemical structures, including self-assembling polyglutamine polypeptides, and (recently) new forays into polysaccharide hydrogels. I will discuss our attempts to dissect complex structural and dynamic features in distinct parts of these repetitive hydrogels, where solvent interactions and surface effects play an important role.

Thursday, January 21, 2021, 3 pm CET

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Dr. Thirupathi Ravula

Dept. of Biophysics and Chemistry, U  Michigan, Ann Arbor

Polymer based lipid-nanodiscs for NMR studies

Abstract:
Membrane proteins play important roles in a variety of cellular functions and also on the pathology of many diseases. High-resolution structural and functional studies on these membrane bound proteins are severely limited by the difficulties associated with their solubilization and reconstitution without a loss of their function. Several membrane mimetics like liposomes, bicelles, micelles, ampiphols, and nanodisc have been developed in an attempt to study membrane proteins in native-like cell membrane environment. Polymer-based nanodiscs are valuable tools in biomedical research that can offer a detergent-free solubilization of membrane proteins maintaining their native lipid environment. In spite of the recent advances in the development and usage of polymer lipid nanodisc systems, lack of control over size and poor tolerance to pH and divalent metal ions are major limitations for further applications. In this presentation, I will discuss about the design, synthesis, demonstration of polymer nanodiscs formation, magnetic-alignment, and feasibilities of solution and solid-state NMR experiments. Our results demonstrate the first use of magnetic-alignment behavior of lyotropic liquid crystalline polymer macro-nanodiscs (> 20 nm in diameter) for solid-state NMR studies on membrane proteins and also as a novel alignment medium for the measurement of RDCs using high resolution NMR. Use of ³¹P, ¹⁴N, TROSY-HSQC, natural abundance ¹⁷O NMR applications will also be presented. The easy preparation of macro-nanodiscs, high stability against pH, divalent metal ions, and high homogeneity are the key advantages for studies to investigate a wide range of molecular systems including natural products, proteins and RNA

Prof. Dr. Timothy P. Lodge

Depts. of Chemistry and Chemical Engineering & Materials Science, U. Minnesota, Minneapolis

Equilibration and Dynamics in Block Copolymer Micelles

Abstract:
While block copolymers generally adopt the morphologies familiar in small molecule surfactants and lipids (i.e., spherical micelles, worm-like micelles, and vesicles), one key difference is that polymeric micelles are typically not at equilibrium. The primary reason is the large number of repeat units in the insoluble block, which makes the thermodynamic penalty for extracting a single chain (“unimer exchange”) substantial. As a consequence, the critical micelle concentration (CMC) is rarely accessed experimentally; however, in the proximity of a critical micelle temperature (CMT), equilibration is possible. We will describe measurements using time-resolved neutron scattering, dynamic light scattering, small-angle X-ray scattering, and liquid-phase TEM to follow chain exchange and micelle fragmentation processes in detail.

Thursday, February 4, 2021, 3 pm CET

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Prof. Dr. Mark D. Ediger

Dept. Chemistry, U Wisconsin, Madison

Using deformation-induced mobility to drive up and down the potential energy landscape of polymer glasses

Abstract:
While mechanical deformation can accelerate segmental dynamics in  polymer glasses by orders of magnitude, it is not so clear what is the  “state” of the polymer glass after deformation.  Such driven  nonequilibrium systems sometimes are  left higher on the potential energy landscape (rejuvenation) but, more  interestingly, sometimes end up lower (overaging).  I describe recent  experiments that track segmental dynamics during and after deformation  in order to find the conditions under which  overaging can occur.

Prof. Dr. Eduardo de Azevedo

Inst. of Physics, U Sao Paulo at Sao Carlos, Brasil

Exploring changes on the polymer dynamics for probing natural and induced structural degradation

Abstract:
Structural degradation of polymers can significantly affect their mechanical properties and their long term uses. Dipolar based time domain NMR at low magnetic field (dipolar TDNMR) provides many techniques capable of probing molecular dynamics and microstructure of polymer materials. This makes these methods good candidates for probing the effect of polymer degradation by monitoring changes in the molecular dynamics and local microstructure, which sometimes occurs without major changes in the chemical composition of the materials.  We will discuss the use of dipolar TDNMR methods, such dipolar echoes, dipolar filters and double quantum build ups, to probe natural and induced degradation of polymer of industrial relevance. This includes the effects of long term ambient exposure in high voltage PDMS rubber electrical insulators add effects of H2S scavengers on polyamide polymers used in flexible oil pipes. In all aforementioned studies we show that dipolar TDNMR is able to provide important featured information difficult to be achieved by other characterization methods.

Thursday, February 18, 2021, 3 pm CET

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Prof. Dr. Sebastian Seiffert

Dept. Chemie, U Mainz

Thermoresponsive Hydrogels for Energy-Autonomous Seawater Desalination

Abstract:
Climate change is the greatest challenge in mankind’s history, and  it will be THE task of our whole society to master this crisis in the  coming years and decades.  Polymer science can make contributions to  this challenge in numerous ways.  This talk  addresses one of these ways: hydrogel-based systems for  energy-autonomous seawater desalination to avert freshwater shortage in  regions like the Middle East.

Prof. Dr. Yaroslav Khimyak

School of Pharmacy, U of East Anglia

Probing organisation of soft matter using NMR spectroscopy: from supramolecular hydrogels to biomaterials

Abstract:
Understanding of the fine  details of self-assembly of building blocks into complex hierarchical  structures represents a major challenge en route to the design and preparation of soft matter materials  with specific properties.  Using examples of supramolecular and  carbohydrate particulate hydrogels, we will aim to combination of  advanced solid-state, high-resolution solution and MAS NMR  methodologies along with the insights from diffraction methods,  rheology and computational methods can provide unique molecular level  details of the organisation of soft matter systems.

Thursday, March 4, 2021, 3 pm CET

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Prof. Dr. Sanat K. Kumar

Chemical Engineering, Columbia U

Nanoparticle Assembly and its role on the Behavior of  Rubber Networks

Abstract:
By now it is well accepted that the addition of filler nanoparticles (NPs, e.g., silica, carbon black) is central to reinforcing rubber – i.e., increasing its modulus, varying loss and reducing wear. To this point in time the incorporation of such NPs into a rubber is carried out during processing. The resulting filler dispersion and hence properties are controlled by a poorly understood combination of filler chemistry, initial filler agglomeration state and processing conditions. We set out to systematically vary the dispersion state of NPs in the uncrosslinked state, study how it is affected by crosslinking and then the consequences of these different dispersion states on linear and non-linear mechanical properties of the filled rubber. This study represents a progress report that has many new results on this topic from my group – I will present these results with the hope that experts in the field can offer us ideas as to how to understand them and what the next critical experiments should be to critically delineate the underlying mechanisms of reinforcement in this important class of materials.

Prof. Dr. Marco Geppi

Chemistry and Industrial Chemistry, U of Pisa

Unravelling the complexity of polymer nanocomposites by Solid State NMR spectroscopy and relaxometry

Abstract:
The combined use of different Solid State NMR approaches to achieve precious molecular information on polymer nanocomposites will be discussed through some case studies. The experimental techniques concern high- and low-resolution spectroscopy, as well as relaxometry. The investigated properties range from phase behaviour to molecular dynamics to physical and chemical interactions at the interfaces. The case studies will cover different types of nanocomposites and, in particular, polymeric matrices filled with inorganic nanoparticles and amorphous biopolymers-organic molecules blends.

Thursday, March 18, 2021, 3 pm CET

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Prof. Dr. Ali Dhinojwala

Polymer Science and Engineering, U Akron

Probing Buried Polymer Interfaces using Interface-Sensitive Nonlinear Optical Spectroscopy

Abstract:
Polymer interfaces control many properties such wetting, adsorption, adhesion, friction, and mechanical properties, and understanding interfacial interactions has remained of central importance for years. In my talk, I discuss the measurements of interfacial interactions (van der Waals and ’polar’ acid-base) by measuring shifts in hydrogen bonding peaks using interface-sensitive sum frequency generation spectroscopy (SFG). Examples will be provided on how the strength of the interfacial interactions influences polymer adsorption from solutions, segregation from polymer blends, and durability and adhesion strength of coatings and adhesives.

Dr. Torsten Gutmann

Inorganic and Physical Chemistry, TU Darmstadt

Solid-state NMR and Dynamic Nuclear Polarization - A powerful tool to study chemical modifications of cellulose based functional materials

Abstract:
The technique of Dynamic Nuclear Polarization (DNP) is introduced to significantly boost sensitivity in solid-state NMR. This enables the detection of low concentrated surface species as well as of low sensitive nuclei such as 15N in natural abundance in functionalized materials. Modified cellulose based materials that can be used in sensorics, microfluidics or optical applications are focused in the presentation.

Thursday, Apri 8, 2021, 4 pm CEST

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Prof. Dr. Quan Chen

ChangChun CAS Institute of Applied Chemistry

Molecular Rheology of Associative Polymers

Abstract:
This  presentation places a focus on the stretchability of associative polymers upon application of the fast elongational flow (with Weissenberg number much larger than one). We examined in detail how the  stretchability was affected by (1) changing the number density of associative groups, (2) tuning the association energy, and (3) introducing a secondary weaker association.

Prof. Dr. Kay Saalwächter

Institut für Physik, Martin-Luther-Univ. Halle

Hierarchical sticker and sticky chain dynamics in transient elastomers for self-healing applications

Abstract:
We  study the relations between the microscopic dynamics and the mechanical behavior of different types of transient elastomers based upon poly(isobutylene) with sticky groups forming clusters in the nm range, namely ionic side groups or hydrogen-bonding terminal  groups. The  dynamics of the chains and of the sticky groups were  studied by a combination of dielectric spectroscopy (DS) and advanced  NMR methods,  and are correlated with the rheological behavior.

Thursday, Apri 22, 2021, 4 pm CEST

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Prof. Dr. Liangbin Li

National Synchrotron Radiation Lab, Univ. of Science and Tech. of China, Hefei

Flow-Induced Crystallization of Polymers during Multi-Axial Deformation

Abstract:
Flow- or stretch-induced  crystallization (FIC or SIC) is believed to be mainly responsible for the excellent mechanical  properties of polymers during real service conditions. In this presentation, the FIC  behaviors of polymers (i.e. natural rubber and polyethylene) during multi-axial deformation like biaxial stretching, film blowing and  balloon blowing  will be presented with the assistance of synchrotron  radiation X-ray scatterings. Considering the phenomenon of frustrating  SIC for natural rubber during biaxial stretching, here we proposed a new model for SIC based on  the results of theoretical calculation, which decouples the free energy contributions of chain orientation from that of conformational entropy reduction.

Dr. Dean DeLongchamp

Material Measurement Laboratory, NIST, Gaithersburg, MD, USA

Polarized resonant soft X-ray scattering measurements in semicrystalline polymers

Abstract:

Orientation and conformation in nanoscale  amorphous regions often dominates the properties of soft materials such  as composites and semicrystalline polymers. Robust correlations between  between structure in these amorphous regions and  important properties are not well developed due to a lack of  measurements with high spatial resolution and a sensitivity to molecular  orientation. I will describe our approach to solving this issue using  polarized resonant soft X-ray scattering (P-RSoXS),  which combines principles of soft X-ray spectroscopy, small-angle  scattering, real-space imaging, and molecular simulation to produce a  molecular scale structure measurement for soft materials and complex  fluids.

Because P-RSoXS is new to the soft material  community, I will first cover the basics of the measurement. The  fundamental principles of P-RSoXS and near-edge X-ray absorption fine  structure (NEXAFS) spectroscopy, the spectroscopic basis  for P-RSoXS, will be reviewed. The P-RSoXS experiment will be discussed  including sample preparation and constraints, which differ considerably  from analogous scattering techniques such as conventional small-angle  X-ray scattering (SAXS) and small angle neutron  scattering (SANS). I will also cover approaches for including gases or  liquids in the experiment, and describe available measurement  facilities. Data collection best practices will be reviewed.

I will then describe polarized resonant soft  X-ray scattering (P-RSoXS) measurements of model systems including  semicrystalline polymers. Analysis will focus on quantitative extraction  of orientation details from nanoscale glassy regions.  This work is now accelerated by a powerful analysis framework using  parallel computation across graphics processing units (GPUs) for the  forward-simulation of P-RSoXS patterns. Certain model systems have been  amenable to quantitative fitting of orientation  parameters using this approach. I will conclude with a discussion of  the broad prospects for P- RSoXS measurements informing and guiding the  processing and synthetic design of soft materials.

Thursday, May 6, 2021, 4 pm CEST

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Prof. Dr. Roberto Simonutti

Dept. Materials Science, U Milano-Bicocca

Xenon the explorer of free volume: ¹²⁹Xe NMR in polymer science

Abstract:
¹²⁹Xenon Nuclear Magnetic Resonance Spectroscopy (NMR) is an exceptional technique for studying many classes of materials. The chemical shift of xenon diffusing in zeolites, clathrates and clays can outline existing cavities and channels and provides information on their size, shape and chemical nature. More recently we extended the application of ¹²⁹Xe NMR to Room Temperature Ionic liquids (RTILs), in this case the chemical shift of xenon can be correlated with the dynamic free volume and compared with data obtained with other techniques as Positron Annihilation Lifetime Spectroscopy (PALS) and Small Angle X-Ray Scattering (SAXS). Regarding macromolecules, ¹²⁹Xe NMR can provide different information depending upon the morphology of the polymer; for bulk polymers it is possible to determine the dimension of free volume of the amorphous phase, the glass transition temperature and eventually the diffusion coefficient. In the case of porous polymers, we can determine both the permanent porosity and the dynamic free volume generated by chain motion in the amorphous phase. Finally, a case of molecularly imprinted polymers (MIP) will be discussed in detail.

Prof. Dr. Jeremiah Johnson

Dept. of Chemistry, MIT, Cambridge

Polymer networks with metal–organic cage junctions

Abstract:
Metallosupramolecular assembly is a powerful tool for the synthesis of porous supramolecules  (e.g., metal-organic cages/polyhedra) and materials (e.g., metal-organic frameworks). This talk will highlight our recent efforts  to integrate metallosupramolecular assembly with traditional polymers to  produce hybrid polymer networks with unique junction structures and properties.

Thursday, May 20, 2021, 4 pm CEST

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Prof. Dr. Ralph Colby

Dept. Materials Science and Engineering, Penn State U, State College

Shear-induced nematic phase in entangled rod-like PEEK melts

Abstract:
We present novel rheo-optical evidence for a shear-induced isotropic-nematic transition exhibited by poly(ether ether ketone) (PEEK) melts of various chain lengths. The key factor is the significant rigidity of the PEEK chain that makes it a rod-like polymer and at low shear rates PEEK is an isotropic rodlike polymer with viscosity scaling as the sixth power of Mw. At high shear rates PEEK is fully nematic and at intermediate shear rates there is a biphase. Consequences of this nematic alignment on crystallization and  mechanical properties will be discussed.

Prof. Dr. Joseph Seymour

Dept. of Chemical and Biological Engineering, Montana State U, Bozeman

Rheo-NMR: LAOS and Microrheology

Abstract:
An overview of Rheo-NMR, which encompasses macroscale velocimetry, mesoscale diffusometry and relaxometry, and microscale spectroscopy will  be presented. MR velocimetry of large amplitude oscillatory shear  (LAOS) Couette flow is shown to  provide spatially resolved transient material response. Measurement of molecular translational and rotational diffusion of solvent provide data  that can be interpreted in terms of microrheology in characterizing heterogeneous dynamics and mesoscale length  scales related to crosslink density in physical polymer gels. True microrheology of particles in dispersions by NMR diffusometry will also be discussed.

Thursday, June 3, 2021, 4 pm CEST

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Prof. Dr. Gillian Goward

Dept. of Chemistry and Chemical Biology, McMaster U, Hamilton, CA

Magnetic Resonance Studies of Ion Transport using both Ex Situ & In Situ Magic Angle Spinning Methods

Abstract:
Understanding mechanisms and trends of Li mobility, diffusion, and aggregation in Lithium Ion Batteries (LIBs) and fuel cells (FCs) is of critical importance in order to characterize the properties of electrodes and electrolytes in functioning cells. This talk will give an overview of the applications of magnetic resonance techniques to such materials, using both ex situ studies of parent materials, as well as in situ studies on functional electrochemical cells. Our group have studied several Li+ and H+ conducting solid-state electrolyte and electrode materials, utilizing a range of magnetic-resonance strategies to compare and quantify ion transport processes. These reveal both the number of local environments involved in exchange, and the diffusion timescales, as a function of temperature.

Prof. Dr. Friedrich Kremer

Molecular Physics, U Leipzig, Germany

Glassy dynamics and charge transport in (polymeric) ionic liquids

Abstract:
Glassy dynamics and charge transport in a variety of bulk glass-forming ionic liquids (ILs) are investigated using a combination of Broadband Dielectric Spectroscopy (BDS), Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR), Differential Scanning Calorimetry and Rheology. While the absolute values of the dc conductivity as well as viscosity vary over more than 11 decades with temperature and upon systematic structural variation of the ILs, quantitative agreement is found between the characteristic diffusion rates and the mechanically measured structural α-relaxation. Based on Einstein, Einstein-Smoluchowski, Maxwell and Langevin relations, the link between rotational and translational diffusion in ILs is experimentally verified and universal scaling of charge transport in ionic liquids is traced back to the dominant role of Brownian dynamics. A further analysis of the dielectric spectra enables one to deduce – using the Einstein-Smoluchowski equation – diffusion coefficients in quantitative agreement with independent PFG NMR results, but in an extraordinarily broad range spanning over 13 decades.

Thursday, June 17, 2021, 4 pm CEST

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Prof. Dr. Iain McKenzie

TRIUMF, Vancouver and Dept. of Chemistry, Simon Fraser U, Burnaby, CA

Probing the Depth Dependence of Dynamics in Polymer Glasses using β-NMR

Abstract:
The observation 27 years ago by Keddie, Jones and Cory that the glass transition temperature of polystyrene thin films decreases with decreasing film thickness led to the suggestion that there is a thin region near the free surface where the polymer motion is faster than in the bulk, but this was not confirmed directly for many years as few techniques can measure how the dynamics varies with distance from the free surface on the nanometre length  scale. I will show that β-detected nuclear magnetic  resonance (β-NMR) of implanted ⁸Li⁺ can be used  to measure the depth and temperature dependence of dynamics on the  nanosecond timescale in polystyrene thin films, which makes it possible to characterize the near-surface region. I will  examine factors that affect the near-surface region, such as the  molecular weight of polystyrene, sample processing and the presence of a  buried interface.

Prof. Dr. Tadanori Koga

Materials Science and Chemical Engineering, SUNY Stony Brook

Local heterogeneities in the structures and dynamics at the solid/polymer interfaces

Abstract:
I will present our recent findings on the local heterogeneities in the interfacial structures and dynamics at the filler/polymer and substrate/polymer interfaces using an integrated experimental and computational approach. I will also discuss how these heterogeneities affect the macroscopic properties of polymer nanocomposites and polymer thin films.

Thursday, July 1, 2021, 4 pm CEST

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Prof. Dr. Niels Holten-Andersen

Dept. of Materials Science & Engineering, MIT

Metal-coordination crosslink dynamics: a bio-inspired toolbox for engineering hydrogel mechanics

Abstract:
Growing evidence supports a critical role of metal-coordination complex crosslinking in a range of desirable soft biological material properties. As such, bio-inspired metal-coordinate crosslink dynamics has been increasingly explored in biomimetic efforts to engineer hydrogel mechanics. Select lessons from our studies in this realm will be presented.

Prof. Dr. Kristin K. Kumashiro

Dept. of Chemistry, University of Hawaii, Honolulu

Strategies for Characterization of Elastin

Abstract:
The elasticity of tissue in vertebrates originates from the protein elastin, but the basis of its functionality is poorly understood. This talk will  provide an overview of our studies, which utilize a novel method of  isotopic enrichment in tandem with solid-state NMR, leading us to an improved model for this biological elastomer.

Thursday, July 15, 2021, 4 pm CEST

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Prof. Dr. Sergei Sheiko

Dept. of Chemistry, U North Carolina at Chapel Hill

Polymer brushes: From molecular imaging to the programmable design of tissue-mimetic materials

Abstract:
Bottlebrush macromolecules uniquely combine properties of molecules and particles. Densely grafted side chains  play multiple oxymoronic roles such as stiffeners of the brush backbone and softeners of polymer networks. Many of the distinct features of brush-like macromolecules can be deduced from molecular imaging with atomic force microscopy. Herein we will present assorted visuals of different brush systems and then discuss their implications for fundamental understanding and practical applications of these unique macromolecules. From many interesting applications, the ability of brush elastomers and gels to precisely replicate the deformation response of soft tissues is particularly noteworthy.

Prof. Dr. Jens-Uwe Sommer

Institute Theory of Polymers, IPF Dresden, Germany

Switchable polymer brushes: Concepts, Simulations and Experiments

Abstract:
Efficient switching of immobilized polymers by environmental parameter changes requires a phase transition in the absence of the translation degrees of freedom of the chains. It is shown that solvents or co-solutes which non-specifically and multiple adsorb on polymers – which we call gluonic solvents – give rise to a new type of phase transition which lead to a discontinuous collapse-reentry scenario in polymer brushes as a response to a continuous change in concentration of the gluonic solvent. Candidates for gluonic solvents are co-nonsolvents, for instance alcohol in aqueous solutions. But also in biological systems such as in the formation of RNA-protein droplets this mechanism is likely to be realized. We have developed a mean-field model for polymers in gluonic solvents and we show that it can be mapped to an effective solvent with a concentration-dependent Flory-parameter. The model can quantitatively predict MD simulations of polymer brushes in the presence of a gluonic solvent, see the figure. Here, also a phase coexistence within the brush can be observed. We carried out systematic experiments on PniPAm brushes of various grafting densities and using a series of alcohols as cosolvents. Using ellipsometry the collapse-reentry transition has been observed and compared with the theory.

Thursday, Sept. 23, 2021, 4 pm CEST

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Prof. Dr. Sindee Simon

Texas Tech and North Carolina State U

The Glass Transition and Structural Recovery:  Pressure-Densified and Pressure-Expanded Glasses and a Test of KAHR Model

Abstract:
The glass transition temperature T_g and structural recovery of glassy PS are investigated using dilatometry and calorimetry.  In this critical analysis of our work and that in the literature, the phenomenology associated with the glass transition, including the cooling rate dependence of the glass transition temperature (T_g) , the apparent activation energy or fragility, and the enthalpic and dilatometric rates of physical aging is reviewed, followed by discussion of the empirical Kovacs-Aklonis-Hutchinson-Ramos (KAHR) and Tool-Narayanaswamy-Moynihan (TNM) models of structural recovery and underlying assumptions.  The structural recovery of pressure-densified (PDG) and, for the first time, pressure-expanded (PEG) glasses are used to test the empirical models.  Both glasses show early devitrification on heating, indicating that these glasses have more mobility, compared to the conventional isobarically-formed glass.  Time permitting, the influence of nanoconfinement, cooling rate, and aging temperature on physical aging will also be discussed in the context of current debates.

Prof. Dr. Wen-Sheng Xu

Changchun Institute of Applied Chemistry, Chinese Academy of Sciences

Entropy Theory of Polymer Glass Formation

Abstract:
The most basic phenomenology of glass-forming polymers is that their dynamics slow down dramatically upon approaching T_g. It has been generally appreciated that the dramatic changes in the dynamics are accompanied by a drop in the fluid entropy and an increase in the extent of collective motion. In this talk, I will discuss the models of glass formation in which the fluid entropy and collective particle motion dominate the theoretical description and data analysis. In particular, the generalized entropy theory (GET) merges an improved lattice model of polymer thermodynamics accounting for molecular structural details and enabling the analytic calculation of the configurational entropy with the Adam-Gibbs model, giving rise to a highly predictive model of the segmental structural relaxation time of polymeric glass-forming liquids. I also discuss the present status of the promising approach to combine the GET and recent string model of polymeric glass-forming liquids into a unified framework.

Thursday, Oct. 21, 2021, 4 pm CEST

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Prof. Dr. Christian Holm

Institue for Computational Physics, U Stuttgart, Germany

Charged Soft Matter— What Computer Simulations can do for you

Abstract:
Computer Simulations have become an indispensable tool to for understanding the physics behind basically all phenomena in nature. Here  I will concentrate on our recent efforts in understanding the structure and dynamics of charged polymers in aqueous solutions, with a focus on  the behaviour of weak polyelectrolytes.

Dr. Ulrich Scheler

Dept. Polyelectrolytes and Dispersions, IPF Dresden, Germany

Polyelectrolytes, charges, counterions and complexes

Abstract:
The combination of diffusion and electrophoresis NMR allows investigating the conformation and effective charge of macromolecules in solution. Using this approach the condensation of counterions on macromolecules is quantified and the formation of complexes of oppositely charged molecules observed.

Thursday, Nov. 18, 2021, 3 pm CET

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Prof. Dr. Wei Yu

Dept. Polymer Science and Engineering, Shanghai Jiao Tong U

Mechanical enhancement and dynamics in polymer nanocomposites

Abstract:
Polymer nanocomposites have broad applications. The size, shape of nanoparticles, and their interaction with polymers determine the mechanical properties of polymer nanocomposites. In this talk, I will discuss the mechanical enhancement and dynamics at different time scales in model polymer nanocomposites using different polymer molecular weights, different particle sizes, and different surface properties of nanoparticles.

Prof. Dr. Rongchun Zhang

South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou

Proton double-quantum solid-state NMR spectroscopy in polymers: from applications to method development

Abstract:
Proton double-quantum (DQ) solid-state NMR spectroscopy has  been widely used in polymers for investigations of polymer structures  and dynamics. In this talk, I would briefly introduce the applications  of DQ NMR for studying polymer network and characterizing hydrogen  bonding interactions. From there, I will also discuss some recent method  development of proton MQ NMR spectroscopy.

Thursday, Dec. 16, 2021, 3 pm CET

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Prof. Dr. Jian Ping Gong

Laboratory of Soft & Wet Matter, Hokkaido University, Sapporo

Yielding Criterion of Double Network Hydrogels

Abstract:
Double network (DN) gels, consisting of the brittle first and the flexible second networks, have  been known as extremely tough hydrogels. In this talk, we will discuss  the relationship between yielding and the first network molecular  structure of DN gels.

Prof. Dr. Erkan Senses

Soft and Active Materials Lab, Koc U, Istanbul

Structure and dynamics of nonlinear polymer-nanoparticle composites

Abstract:
We have designed new types of nanocomposites and blend based on  well-defined non-linear polymer architectures and well-dispersed  nanoparticles. I will overview the key results we obtained from static  and dynamic neutron scattering, x-ray  photon correlation spectroscopy  and bulk rheology, which help to  uncover the distinct role of polymer  topology on (i) dynamics of  polymers at nanoparticle interfaces, (ii)  nanoscale particle motion  polymer matrices, and (iii) bulk rheological  reinforcement.