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225 results on '"Allgaier, Jürgen"'

2. Polyelectrolyte-protein synergism: pH-responsive polyelectrolyte/insulin complexes as versatile carriers for targeted protein and drug delivery

Author

Murmiliuk, Anastasiia, Iwase, Hiroki, Kang, Jia-Jhen, Mohanakumar, Shilpa, Appavou, Marie-Sousai, Wood, Kathleen, Almásy, László, Len, Adél, Schwärzer, Kuno, Allgaier, Jürgen, Dulle, Martin, Gensch, Thomas, Förster, Beate, Ito, Kanae, Nakagawa, Hiroshi, Wiegand, Simone, Förster, Stephan, and Radulescu, Aurel

Published
2024
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4. Structure and dynamics of DOPC vesicles: A transformation from unilamellar to multilamellar vesicles by n-alkyl-PEO polymer

Author

De Mel, Judith U., Gupta, Sudipta, Wilner, Lutz, Allgaier, Jürgen, Stingaciu, Laura R., Bleuel, Markus, and Schneider, Gerald J.

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

We investigate the influence of a non-ionic surfactant like polymer on phospholipid vesicles. Our results from cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), small angle neutron and X-ray scattering (SANS/SAXS), identifies the existence of multilayer vesicles and an increase in size of the vesicles in presence of the polymers. We present a generalized model to obtain the bending rigidity from neutron spin echo spectroscopy (NSE) data for multilayer vesicles. We demonstrated that polymers are trapped in the lipid bilayer, causing a partial disruption in the vesicle, which is attributed to the reduction in bending rigidity per unit bilayer. We also observed substantial dampening of the trapped lipid tail motion in presence of the polymer. Our results highlighted the possibilities of using specialized polymers that can disrupt membrane and control their dynamics with possible application in topical drug or nutraceutical formulations., Comment: 29 pages, 10 figures, in process with ACS. arXiv admin note: text overlap with arXiv:2004.04869

Published
2020

7. Validity of Stokes-Einstein Relation in Soft Colloids up to the Glass Transition

Author

Gupta, Sudipta, Stellbrink, Jörg, Zaccarelli, Emanuela, Likos, Christos N., Camargo, Manuel, Holmqvist, Peter, Allgaier, Jürgen, Willner, Lutz, and Richter, Dieter

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

We investigate the dynamics of kinetically frozen block copolymer micelles of different softness across a wide range of particle concentrations, from the fluid to the onset of glassy behavior, through a combination of rheology, dynamic light scattering and pulsed field gradient NMR spectroscopy. We additionally perform Brownian dynamics simulations based on an ultrasoft coarse-grained potential, which are found to be in quantitative agreement with experiments, capturing even the very details of dynamic structure factors S(Q, t) on approaching the glass transition. We provide evidence that for these systems the Stokes-Einstein relation holds up to the glass transition; given that it is violated for dense suspensions of hard colloids, our findings suggest that its validity is an intriguing signature of ultrasoft interactions., Comment: 5 pages, 4 figures, Supplementary Information, Accepted to Physical Review Letters (PRL) (2015)

Published
2015
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8. Dynamics of polymer electrolyte with LiTFSI via Quasi-Elastic Neutron Scattering

Author

Wang Hui, Osti Naresh C., Allgaier Jürgen, Berg Marcella Cabrera, Halver Rene, Mamontov Eugene, Sutmann Godehard, Doi Yuya, Bucher Nicolas, Egami Takeshi, Förster Stephan, and Ohl Michael

Subjects
Physics, QC1-999
Abstract

Most lithium batteries offer a wide range of applications. However, safety issues are still an unresolved issue for several applications. To solve the safety issue of Li-ion batteries, solid polymer electrolyte is a promising candidate to replace commercial liquid electrolyte. A 4-arm star poly(ethylene oxide) polymer with LiTFSI salt as an electrolyte was studied. The dynamics of this polymer were explored with the Quasi-Elastic Neutron Scattering technique. Furthermore, the influence of temperature and Li salt concentration on the polymer dynamics was investigated. The dynamics of the polymer ends of the arm show much higher flexibility than the core parts making those types of polymers attractive for further studies in battery research.

Published
2023
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11. Extended Q-range small-angle neutron scattering to understand the morphology of proton-exchange membranes: the case of the functionalized syndiotactic-polystyrene model system

Author

Schiavone, Maria-Maddalena, primary, Lamparelli, David Hermann, additional, Daniel, Christophe, additional, Golla, Manuchar, additional, Zhao, Yue, additional, Iwase, Hiroki, additional, Arima-Osonoi, Hiroshi, additional, Takata, Shin-ichi, additional, Szentmiklosi, Laszlo, additional, Maroti, Boglarka, additional, Allgaier, Jürgen, additional, and Radulescu, Aurel, additional

Published
2023
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13. The combination of neutron spin echo and dielectric spectroscopy to examine tube dilation

Author

Malo de Molina Paula, Alegría Angel, Allgaier Jürgen, Kruteva Margarita, Hoffmann Ingo, Prévost Sylvain, Monkenbusch Michael, Richter Dieter, Arbe Arantxa, and Colmenero Juan

Subjects
Physics, QC1-999
Abstract

The polymer dynamics in blends of long and short chains spans several decades in time and the understanding of the effect of the short chains on the relaxation mechanism of the long chains due to constraint release requires the combination of microscopic and macroscopic techniques. While the longtime dynamics can be accessed by mechanical or dielectric spectroscopy (DS), its relation to the microstructural details requires the application of theoretical models. In contrast, neutron spin echo (NSE) measures directly the dynamic structure factor reflecting the process of constraint removal at the molecular scale. Here the comparison of NSE and DS results in a model blend of short and long polyisoprene enables the exploration of the entire time regime showing that constraint release leads to a dilation of the confining tube. We show the description of the dynamic tube dilation using a simple model in which the time controlling the tube dilation for the long chain is the terminal time of the short chain.

Published
2022
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19. Resolving the different bulk moduli within individual soft nanogels using small-angle neutron scattering

Author

Houston, Judith Elizabeth, primary, Fruhner, Lisa, additional, de la Cotte, Alexis, additional, Rojo González, Javier, additional, Petrunin, Alexander Valerievich, additional, Gasser, Urs, additional, Schweins, Ralf, additional, Allgaier, Jürgen, additional, Richtering, Walter, additional, Fernandez-Nieves, Alberto, additional, and Scotti, Andrea, additional

Published
2022
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20. The combination of neutron spin echo and dielectric spectroscopy to examine tube dilation

Author

Ikerbasque Basque Foundation for Science, Eusko Jaurlaritza, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), European Commission, Malo de Molina, Paula, Alegría, Ángel, Allgaier, Jürgen, Kruteva, Margarita, Hoffmann, Ingo, Prévost, Sylvain, Monkenbusch, Michael, Richter, Dieter, Arbe, Arantxa, Colmenero de León, Juan, Ikerbasque Basque Foundation for Science, Eusko Jaurlaritza, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), European Commission, Malo de Molina, Paula, Alegría, Ángel, Allgaier, Jürgen, Kruteva, Margarita, Hoffmann, Ingo, Prévost, Sylvain, Monkenbusch, Michael, Richter, Dieter, Arbe, Arantxa, and Colmenero de León, Juan

Abstract

The polymer dynamics in blends of long and short chains spans several decades in time and the understanding of the effect of the short chains on the relaxation mechanism of the long chains due to constraint release requires the combination of microscopic and macroscopic techniques. While the longtime dynamics can be accessed by mechanical or dielectric spectroscopy (DS), its relation to the microstructural details requires the application of theoretical models. In contrast, neutron spin echo (NSE) measures directly the dynamic structure factor reflecting the process of constraint removal at the molecular scale. Here the comparison of NSE and DS results in a model blend of short and long polyisoprene enables the exploration of the entire time regime showing that constraint release leads to a dilation of the confining tube. We show the description of the dynamic tube dilation using a simple model in which the time controlling the tube dilation for the long chain is the terminal time of the short chain.

Published
2022

26. Poly(ethylene oxide) melt intercalation in graphite oxide: sensitivity to topology, cyclic versus linear chains

Author

Ministerio de Ciencia, Innovación y Universidades (España), Eusko Jaurlaritza, Agencia Estatal de Investigación (España), Diputación Foral de Guipúzcoa, European Commission, Barroso-Bujans, Fabienne, Allgaier, Jürgen, Alegría, Ángel, Ministerio de Ciencia, Innovación y Universidades (España), Eusko Jaurlaritza, Agencia Estatal de Investigación (España), Diputación Foral de Guipúzcoa, European Commission, Barroso-Bujans, Fabienne, Allgaier, Jürgen, and Alegría, Ángel

Abstract

The role of poly(ethylene oxide) (PEO) topology in the melt intercalation in graphite oxide (GO)-based materials is investigated. The intercalation of PEO in GO leads to changes in the GO interlayer space and to the suppression of polymer thermal transitions (crystallization and glass transition). Herein, we perform kinetic measurements of the melt intercalation of cyclic and linear PEO (CPEO and LPEO) with Mn = 2–20 kg/mol in different GO-based structures by monitoring the reduction of melting peak areas of PEO. We demonstrate that high sensitivity to PEO topology can be achieved using GO partially pillared with 1,6-hexanediamine. Using only 1 wt % of pillars, the rate constants of cyclic PEO become up to a 100 times smaller than that of linear chains of similar molecular weight. This enormous difference in the intercalation kinetics of topologically different PEO chains cannot be achieved in nonpillared GO, where the rate constants of cyclic PEO presented values that were only up to 4 times smaller than that of their linear analogues. The dramatic reduction in the intercalation rate for CPEO in the presence of pillars indicates that topological constraints (formation of squeezed structures with double folded strand conformations) are the most important factors affecting the melt intercalation kinetics. The results suggest that it is possible to restrict the intercalation of cyclic PEO into partially pillared GO, whilst allowing the linear analogue to diffuse through the GO interlayer space. This important finding could be the basis for developing new methods of purification of cyclic polymers.

Published
2020

27. Description of poly(ethylenepropylene) confined in nanopores by a modified Rouse model.

Author

Muthmann, Matthias, Krutyeva, Margarita, Willner, Lutz, Allgaier, Jürgen, Richter, Dieter, Zorn, Reiner, Ohl, Michael, Rebbin, Vivian, and Lindner, Peter

Subjects
NANOPORES, NANOSTRUCTURED materials, NEUTRON scattering, POTENTIAL scattering, POLYMERS
Abstract

A recent model for unentangled polymer chains in confinement [M. Dolgushev and M. Krutyeva, Macromol. Theory Simul. 21, 565 (2012)] is scrutinized by small-angle neutron scattering (SANS) with respect to its static prediction, the single-chain structure factor. We find a remarkable agreement although the model simplifies the effect of the confinement to a harmonic potential. The effective confinement size from fits of SANS data with the model agrees well with the actual pore size. Starting from this result we discuss the possibility of an experiment on the dynamic structure factor predicted by the model. It turns out that such an experiment would need a large ratio polymer dimension/pore size which is difficult but not impossible to achieve. [ABSTRACT FROM AUTHOR]

Published
2017
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30. Tube Dilation in Isofrictional Polymer Blends Based on Polyisoprene with Different Topologies: Combination of Dielectric and Rheological Spectroscopy, Pulsed-Field-Gradient NMR, and Neutron Spin Echo (NSE) Techniques

Author

Malo de Molina, Paula, primary, Alegría, Angel, additional, Allgaier, Jürgen, additional, Kruteva, Margarita, additional, Hoffmann, Ingo, additional, Prévost, Sylvain, additional, Monkenbusch, Michael, additional, Richter, Dieter, additional, Arbe, Arantxa, additional, and Colmenero, Juan, additional

Published
2020
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36. Direct observation of dynamic tube dilation in entangled polymer blends: A combination of neutron scattering and dielectric techniques

Author

Eusko Jaurlaritza, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), European Commission, Jülich Research Centre, Malo de Molina, Paula, Alegría, Ángel, Allgaier, Jürgen, Kruteva, Margarita, Hoffmann, Ingo, Prévost, Sylvain, Monkenbusch, Michael, Richter, Dieter, Arbe, Arantxa, Colmenero de León, Juan, Eusko Jaurlaritza, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), European Commission, Jülich Research Centre, Malo de Molina, Paula, Alegría, Ángel, Allgaier, Jürgen, Kruteva, Margarita, Hoffmann, Ingo, Prévost, Sylvain, Monkenbusch, Michael, Richter, Dieter, Arbe, Arantxa, and Colmenero de León, Juan

Abstract

We report a microscopic observation of the time-dependent dynamic tube dilation process on isofrictional bidisperse melts. By applying neutron spin echo (NSE) and dielectric techniques on blends of long polyisoprene (PI) chains with short PI additives with different topology, we access the dynamics of the tube dilation process on a molecular scale. The time-dependent tube dilation is directly revealed by NSE as an additional time dependence of the dynamic structure factor in the local reptation regime. We identify the characteristic time of tube dilation as the terminal time of the additive.

Published
2019

37. Simultaneous small-angle neutron scattering and Fourier transform infrared spectroscopic measurements on cocrystals of syndiotactic polystyrene with polyethylene glycol dimethyl ethers1

Author

Kaneko, Fumitoshi, Seto, Naoki, Sato, Shuma, Radulescu, Aurel, Schiavone, Maria Maddalena, Allgaier, Jürgen, and Ute, Koichi

Subjects
small-angle neutron scattering, Fourier transform IR spectroscopy, simultaneous measurement, sense organs, cocrystals, syndiotactic polystyrene, Research Papers
Abstract

A new simultaneous measurement method combining small-angle neutron scattering and Fourier-transform infrared spectroscopy was applied to a study on a syndiotactic polystyrene cocrystal with polyethylene glycol dimethyl ether with a molecular weight of 500. It is suggested that the guest molecules in the crystalline region have an elongated structure along the thickness direction of the crystalline lamellae., Syndiotactic polystyrene (sPS) is a crystalline polymer which has a unique property; it is able to form cocrystals with a wide range of chemical compounds, in which the guest molecules are confined in the vacancies of the host sPS crystalline region. Recently, it has been found that even polyethylene glycol oligomers with a molecular weight of more than several hundreds can be introduced into the sPS crystalline region. It is quite important to know how such a long-chain molecule is stored in the host sPS lattice. To tackle this issue, a new simultaneous measurement method combing small-angle neutron scattering and Fourier transform infrared spectroscopy (SANS/FTIR), which has been recently developed by the authors, was applied to an sPS cocrystal with polyethylene glycol dimethyl ether with a molecular weight of 500 (PEGDME500). The temperature-dependent changes of the SANS profile and FTIR spectrum were followed from room temperature up to 413 K for a one-dimensionally oriented SANS/PEGDME500 cocrystal sample. The intensity of the reflections due to the stacking of crystalline lamellae showed a significant temperature dependence. The two-dimensional pattern in the high Q region of SANS also changed depending on temperature. The combined information obtained by SANS and FTIR suggested that PEGDME500 molecules are distributed in both the crystalline and amorphous regions in the low-temperature region close to room temperature, but they are predominantly included in the amorphous region in the high-temperature region. It was also suggested by the two-dimensional SANS profile that PEGDME500 molecules in the crystalline region have an elongated structure along the thickness direction of the crystalline lamellae.

Published
2016

39. Effect of the nanofiller topology on the dynamics of all-polymer nanocomposites

Author

Malo de Molina, Paula, Kruteva, Margarita, Allgaier, Jürgen, Alegría, Ángel, Richter, Dieter, Arbe, Arantxa, Colmenero de León, Juan, Malo de Molina, Paula, Kruteva, Margarita, Allgaier, Jürgen, Alegría, Ángel, Richter, Dieter, Arbe, Arantxa, and Colmenero de León, Juan

Abstract

Nanoparticles are added to polymeric matrices to form nanocomposites with enhanced mechanical, optical or& electrical properties. The performance and macroscopic properties of polymer nanocomposites depend on the dynamics of the polymer matrix affected by the filler topology and concentration. However, despite the efforts, the confinement effects of nanoparticles on polymer motions are still not fully understood, especially in the case of soft nanoparticles. Recently, a notable dilation of the entanglement tube diameter in polyethyleneoxide (PEO) linear chains when mixed with poly(methylmethacrylate) (PMMA) single-chain nano-particles (SCNPs) was observed. In that case, however, the two components have a large dynamic asymmetry, being the PMMA SCNPs frozen compared to PEO. To isolate the topology effect we studied systems where the polymer matrix and the filler have the same chemistry (polyisoprene) and thus are dynamically symmetric. We have done a systematic variation of the filler topology and concentration and probed the polymer matrix chain dynamics using a combination of PFG-NMR and dielectric spectroscopy. We used two star polymers with 8 and 18-arms and compared them to the linear case of the same size, i.e. 2 arms. Our results show an acceleration&of&the& linear matrix chain mobility with the additive concentration, but less so with the additive topology.

Published
2018

44. Dynamic properties of microemulsions modified with homopolymers and diblock copolymers: The determination of bending moduli and renormalization effects.

Author

Holderer, Olaf, Frielinghaus, Henrich, Byelov, Dmytro, Monkenbusch, Michael, Allgaier, Jürgen, and Richter, Dieter

Subjects
COPOLYMERS, SURFACE active agents, MOLECULAR weights, SPECTRUM analysis, POLYMERS, PHYSICAL & theoretical chemistry
Abstract

The properties of bicontinuous microemulsions, consisting of water, oil, and a surfactant, can be modified by the addition of diblock copolymers (boosting effect) and homopolymers (inverse boosting effect) or a combination of both. Here, the influence of the addition of homopolymers (PEPX and PEOX, X=5k or 10k molecular weight) on the dynamics of the surfactant layer is studied with neutron spin echo spectroscopy (NSE). Combining the results with the previous findings for diblock copolymers allows for a better separation of viscosity and bending modulus effects. With the addition of homopolymers, a significant increase of the relaxation rate compared to the pure microemulsion has been observed. The influence on the bending rigidity κ is measured with NSE experiments. Homopolymer addition reduces κ by up to Δκ≃-0.5kBT, whereas the diblock copolymer yields an increase of κ by ∼0.3kBT. Comparison of the bending moduli that are obtained by analysis of the dynamics to those obtained from small angle neutron scattering (SANS) sheds light on the different renormalization length scales for NSE and SANS. Variation of the surfactant concentration at otherwise constant conditions of homopolymer or diblock-copolymer concentration shows that NSE results are leading to the pure bending rigidity, while the renormalized one is measured with SANS. [ABSTRACT FROM AUTHOR]

Published
2005
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47. Nanocomposites of Highly Monodisperse Encapsulated Superparamagnetic Iron Oxide Nanocrystals Homogeneously Dispersed in a Poly(ethylene Oxide) Melt

Author

Feld, Artur, primary, Koll, Rieke, additional, Fruhner, Lisa Sarah, additional, Krutyeva, Margarita, additional, Pyckhout-Hintzen, Wim, additional, Weiß, Christine, additional, Heller, Hauke, additional, Weimer, Agnes, additional, Schmidtke, Christian, additional, Appavou, Marie-Sousai, additional, Kentzinger, Emmanuel, additional, Allgaier, Jürgen, additional, and Weller, Horst, additional

Published
2017
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49. Role of dynamic asymmetry on the collective dynamics of comblike polymers: Insights from neutron spin-echo experiments and coarse-grained molecular dynamics simulations

Author

Ministerio de Economía y Competitividad (España), Eusko Jaurlaritza, Heinz Maier-Leibnitz Zentrum, European Commission, Arbe, Arantxa, Moreno Segurado, Ángel J., Allgaier, Jürgen, Ivanova, Oxana, Fouquet, Peter, Colmenero de León, Juan, Richter, Dieter, Ministerio de Economía y Competitividad (España), Eusko Jaurlaritza, Heinz Maier-Leibnitz Zentrum, European Commission, Arbe, Arantxa, Moreno Segurado, Ángel J., Allgaier, Jürgen, Ivanova, Oxana, Fouquet, Peter, Colmenero de León, Juan, and Richter, Dieter

Abstract

We investigate the collective dynamics of comblike polymers displaying nanosegregation in side groups and main-chain rich domains, where side groups and backbones are dynamically equivalent. Neutron spin-echo experiments on poly(alkylene oxide)s with increasing side-group length have been focused on the decay of inter- and intradomain correlations and are complemented with molecular dynamics simulations on a coarse-grained model. In general, a good qualitative agreement between simulation and experiment is found. The collective times at inter- and intradomain levels converge with decreasing temperature, implying a common glass transition, and separate at high temperatures, revealing an increasing role of connectivity. The features of collective relaxations—regarding stretching, characteristic time, and temperature dependence—are independent of branching. The standard stretching for side-group motions and the closeness of collective and self-motions show that the anomalies exhibited by dynamically asymmetric comblike macromolecules disappear.

Published
2016

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