Article
Chemistry, Physical
I. V. Brekotkin, N. F. Fatkullin, K. Lindt, C. Mattea, S. Stapf
Summary: This article introduces the spatial displacements of spins and their impact on the DQ Hamiltonian in a double-quantum nuclear magnetic resonance pulse sequence. It provides a simple expression for estimating and controlling the contributions to the initial rise of the DQ build-up function by varying experimental parameters. The application of polymers is also discussed.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Polymer Science
William S. Fall, Jorg Baschnagel, Olivier Lhost, Hendrik Meyer
Summary: The role of short chain branches (SCBs) on the melt and crystalline properties of monodisperse polyethylene systems has been investigated. Molecular dynamics simulations were used to study the influence of different numbers of SCBs on the melt and crystalline properties. It was found that the behavior of each system during crystallization varied considerably depending on the cooling rate and number of branches. The introduction of SCBs allows control over the lamella thickness and opens up opportunities for studying more complex chain architectures and mimicking industrial polyethylene morphologies.
Article
Polymer Science
Yexin Zheng, Mesfin Tsige, Shi-Qing Wang
Summary: In this study, molecular dynamics simulations were used to investigate the entanglement lockup phenomena in the uniaxial melt stretching of entangled polymer melts. The results revealed that under high strains, the entanglement network became increasingly tighter, leading to chain tension and the formation of network junctions. It was hypothesized that the interchain entanglement at junctions can lockup as long as certain conditions are met. This study provides insights into the mechanical properties of polymer materials.
MACROMOLECULAR RAPID COMMUNICATIONS
(2023)
Article
Polymer Science
Seung Heum Jeong, Soowon Cho, Chunggi Baig
Summary: This study presents a detailed analysis of the scaling behavior of chain rotation dynamics in shear flow for melt and dilute linear polymer systems. The results show that dilute systems with hydrodynamic interaction (HI) and excluded volume (EV) effects exhibit two distinct scaling behaviors of chain rotation time between the intermediate and strong flow regimes. In contrast, free-draining dilute polymer systems display a simpler single-scaling behavior throughout the intermediate-to-strong flow regimes. The combined HI and EV effects weaken the structural change of polymer chains and enhance chain rotation dynamics by disturbing chain stretch and alignment to the flow direction. The presence of intermolecular interactions between chains in melt systems leads to two distinct scaling behaviors of chain rotation time as well. The overall scaling behavior of chain rotation is determined by the kinematically stable angular regions near the flow direction, while the kinematically unstable angular regions exhibit affine chain rotation dynamics. This study provides important insights into the understanding of chain rotation dynamics in shear flow.
Article
Mechanics
Martin Zatloukal, Jiri Drabek
Summary: The monomeric friction coefficient for fully aligned chains was determined for three linear isotactic polypropylene melts, showing a significant reduction compared to the equilibrium friction coefficient. This supports the argument that a reduction in the friction coefficient is necessary to understand the dynamics of polymer melts in very fast flows, as suggested by recent rheological data and molecular simulations.
Article
Polymer Science
Nicholas F. Mendez, Deboleena Dhara, Qingteng Zhang, Suresh Narayanan, Linda S. Schadler, Alejandro J. J. Muller, Sanat K. Kumar
Summary: X-ray photon correlation spectroscopy measurements were used to analyze the dynamics of bare and bimodal grafted silica nanoparticles mixed with PEO melts. The results showed diffusive behavior of the nanoparticles in dilute polymer nanocomposite samples, taking into account the adsorbed PEO polymer layer. The dynamics of grafted nanoparticles were found to be influenced by morphology and grafting parameters at larger scales.
Article
Chemistry, Physical
R. E. Ryltsev, N. M. Chtchelkatchev
Summary: This paper discusses the use of machine learning interatomic potentials (MLIPs) in materials simulations. Using the ternary Al-Cu-Ni metallic melts as an example, the authors construct a many-body deep machine learning potential that accurately describes both the atomic structure and dynamics of the system across the entire composition range. The developed MLIP demonstrates good compositional transferability.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Polymer Science
Jon Maiz, Ester Verde-Sesto, Isabel Asenjo-Sanz, Paula Malo de Molina, Bernhard Frick, Jose A. Pomposo, Arantxa Arbe, Juan Colmenero
Summary: In this study, the impact of internal cross-links on the properties of polymer melts was investigated using various techniques. It was found that internal cross-links do not significantly alter local properties and fast dynamics, but do slow down the alpha-relaxation process. Additionally, broader response functions and stronger deviations from Gaussian behavior were observed in the SCNPs melt, hinting at additional heterogeneities. Furthermore, rheological properties were clearly affected by internal cross-links.
Article
Physics, Condensed Matter
M. Leticia Rubio Puzzo, Ernesto S. Loscar, Andres De Virgiliis, Tomas S. Grigera
Summary: The study investigates the short-time dynamics of Vicsek model with vector noise and finds that despite the non-equilibrium characteristics, the short-time dynamics presents similar phenomenology to equilibrium systems. The study shows that the transition can be determined as continuous or discontinuous, and the critical point and critical exponents can be determined in continuous transitions.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Chemistry, Multidisciplinary
Sophia Y. Chan, Mayank Jhalaria, Yucheng Huang, Ruipeng Li, Brian C. Benicewicz, Christopher J. Durning, Thi Vo, Sanat K. Kumar
Summary: Polymer-grafted nanoparticle membranes show unexpected gas transport enhancements, but the structural origins of this behavior are unclear. This study measured and interpreted data on grafted nanoparticles and found that as the graft molecular weight increases, the gas transport enhancement decreases.
Article
Polymer Science
Fan Wang, Lu-Kun Feng, Ye-Di Li, Hong-Xia Guo
Summary: Dissipative particle dynamics (DPD) is a promising method for studying entangled polymers, but its applicability as a model for ideal chains and accurate description of entangled melts is not well understood. In this study, we comprehensively investigate the structure, dynamics, and linear viscoelasticity of a DPD entangled model system, specifically a semiflexible linear polymer melt. Our results show that the DPD model accurately predicts the monomer motion and relaxation behavior of entangled polymers, following the predictions of reptation theory. However, there are some limitations to the reptation theory, as evidenced by anomalous sub-diffusive motion and cross-correlation between chains. Overall, the semiflexible linear DPD model is able to capture the static and dynamic properties of entangled polymer melts.
CHINESE JOURNAL OF POLYMER SCIENCE
(2023)
Article
Polymer Science
Ralm G. Ricarte, Sachin Shanbhag
Summary: Vitrimers are polymer networks that undergo dynamic associative exchange reactions, exhibiting unique structure-viscoelasticity relationships. Utilizing a sticky Rouse model, the study explores the structure-viscoelasticity characteristics of unentangled vitrimer melts. The findings reveal that the structure and temperature significantly impact the zero-shear viscosity and characteristic relaxation time of vitrimers.
Article
Engineering, Mechanical
B. C. N. M. de Castilho, N. Sharifi, S. A. Alidokht, K. Harrington, P. Stoyanov, C. Moreau, R. R. Chromik
Summary: NiCr-Cr2O3-Ag-BaF2/CaF2 (PS304) and NiMoAl-Cr2O3-Ag-BaF2/CaF2 (PS400) coatings exhibit low wear and friction at temperatures ranging from 25 to 700 degrees C. However, the formation of small precipitates in high temperatures due to expansion of NiCr matrix component can pose challenges for coating integrity in gas turbine applications. Experimental evidence suggests that the precipitates are formed by fluorine diffusing from fluorides to NiCr, driven by oxidation of the fluorides to form BaCrO4 and CaCrO4. PS400 coatings show superior thermal stability and wear resistance compared to PS304 coatings under tested conditions.
Article
Engineering, Environmental
Jiankai Ge, Baron Peters
Summary: Various heterogeneous catalysts are being developed for plastic recycling, most of which operate in viscous polymer melts. The external mass transfer effects in these melts can inhibit the supply of co-reactants and the diffusion of long chain products away from the catalyst after each cut. This can unintentionally confer processivity to catalyst operation.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Yuri N. Starodubtsev, Vladimir S. Tsepelev, Nadezhda P. Tsepeleva
Summary: The study found that there is a linear relationship between the kinematic viscosity and temperature for multicomponent melts of nanocrystalline soft magnetic alloys. The activation energy of viscous flow is linearly related to the cluster size and the melt viscosity increases with decreasing cluster size. The change in the Arrhenius plot on the temperature dependence of viscosity in the anomalous zone suggests a liquid-liquid structure transition.
Article
Polymer Science
Wei Li, Pritam K. Jana, Alireza F. Behbahani, Georgios Kritikos, Ludwig Schneider, Patrycja Polinska, Craig Burkhart, Vagelis A. Harmandaris, Marcus Mueller, Manolis Doxastakis
Summary: A hierarchical triple-scale simulation methodology is applied to investigate the dynamics of cis-1,4 polyisoprene melts, showing good agreement with experimental data, especially for highly entangled polymer melts. The study provides parameter-free predictions on the dynamics of polymeric materials.
Article
Polymer Science
Marcus Mueller
Summary: This study investigates the structure and dynamics of loops and bridges in the lamellar phase of symmetric ABA triblock copolymers, revealing a linear correlation between bridge fraction and the average variance of the first Rouse mode. The system is proposed to be a mixture of noninteracting loops and bridges with a two-state Markov dynamics. Multichain simulations show an extremely long relaxation time, which can be accelerated using the heterogeneous multiscale method.
Article
Chemistry, Physical
Marcus Mueller
Summary: Using analytical considerations and particle-based simulations, this study investigates the relaxation of a density modulation in a polymer system without nonbonded interactions. The results demonstrate that shallow density modulations, prepared by different processes but with identical amplitudes and wavevectors, exhibit different nonexponential decay behaviors, challenging the assumption that density alone characterizes the polymer system configuration. Analytic descriptions within Linear-Response Theory (LRT) and the Rouse model are provided, showing quantitative agreement with the particle-based simulations.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Polymer Science
Cody T. Bezik, Joshua A. Mysona, Ludwig Schneider, Abelardo Ramirez-Hernandez, Marcus Mueller, Juan J. de Pablo
Summary: A new mesophase in binary blends of A-b-(BA')3 miktoarm star block copolymers and A homopolymers has been discovered, consisting of aperiodic discrete domains of A embedded in a continuous matrix of B. Molecular bridging dominates the mechanical behavior of the mesophase, outweighing the influence of microphase segregation. The application of shear leads to a closer structure resembling its speculated discrete nature.
Article
Polymer Science
Gaoyuan Wang, Marcus Mueller
Summary: This study investigates the interplay between elasticity and microphase separation in quasi-two-dimensional phantom networks formed by AB diblock copolymers. Computer simulations and phenomenological considerations show that network elasticity has a minor role in the system when the stretching is weak. As the stretching increases, the incompatibility for the order-disorder transition decreases, and a multigrain state with tilted lamellae is observed at intermediate stretching.
Article
Polymer Science
Louis Pigard, Debashish Mukherji, Jorg Rottler, Marcus Mueller
Summary: Thermal transport properties of materials play a crucial role in various applications, with polymers offering different energy transport pathways due to their distinct microscopic interactions. A simple analytical model is devised to separate the microscopic bonded and nonbonded contributions to heat transport in polymeric materials, showing potential for tailored thermal conductivity through macromolecular engineering. Molecular simulations validate the model's ability to describe thermal transport and suggest strategies for modifying the thermal transport coefficient of polymeric materials.
Article
Chemistry, Physical
David Steffen, Ludwig Schneider, Marcus Mueller, Joerg Rottler
Summary: This paper investigates the spatiotemporal autocorrelation of shear stress in a supercooled fluid close to the glass transition using molecular dynamics simulations. The results show anisotropic correlations and strongly damped oscillations at non-zero wavevectors. The experimental findings are in good quantitative agreement with a recently developed hydrodynamic theory.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Polymer Science
Gaoyuan Wang, Annette Zippelius, Marcus Mueller
Summary: Cross-linking is a versatile strategy to stabilize the structure and control the dynamics of polymers. This study systematically investigates the phase behavior of randomly cross-linked diblock copolymer melts and reveals the significant influence of the preparation state on the phase diagram.
Article
Polymer Science
Pritam Kumar Jana, Petra Bacova, Ludwig Schneider, Hideki Kobayashi, Kai-Uwe Hollborn, Patrycja Polinska, Craig Burkhart, Vagelis A. Harmandaris, Marcus Mueller
Summary: The theological properties of polymer composites depend on the interfacial interactions between solid fillers and a polymer fluid. This study presents a simulation strategy called the wall-spring thermostat, which uses transient bonds to mimic the interactions between the polymer and the solid surface. The density and lifetime of these transient bonds can be adjusted to control the single-chain and collective dynamics of the polymer at the surface. The simulation technique allows for the capture of dynamic heterogeneities at surfaces.
Article
Chemistry, Physical
Kai-Uwe Hollborn, Ludwig Schneider, Marcus Muller
Summary: Highly coarse-grained (hCG) linear polymer models, based on dissipative particle dynamics (DPD), allow for studying long time and length scales. This top-down strategy uses relevant interactions, such as molecular connectivity, and coarse-grained invariants, like the mean-squared end-to-end distance, to describe the equilibrium behavior of long, flexible macromolecules. However, describing the dynamics of long, entangled polymers is challenging because hCG models do not enforce the noncrossability of molecular backbones. One technique to mimic entanglements in hCG models is slip-springs, which has shown quantitative agreement with simulations, experiments, and theoretical predictions.
JOURNAL OF PHYSICAL CHEMISTRY B
(2022)
Article
Polymer Science
Oliver Dreyer, Gregor Ibbeken, Ludwig Schneider, Niklas Blagojevic, Maryam Radjabian, Volker Abetz, Marcus Mueller
Summary: In this study, the self-assembly of asymmetric diblock copolymers during solvent evaporation was investigated using particle-based Monte Carlo simulations and continuum modeling. The effects of evaporation rate and solvent selectivity on structure formation, particularly the alignment of minority block cylinders, were examined. Comparing the two simulation techniques helped identify general trends with parameter variation and understand the role of single-chain dynamics, fluctuations, and additional model details.
Article
Chemistry, Physical
Felix Weissenfeld, Lucia Wesenberg, Masaki Nakahata, Marcus Mueller, Motomu Tanaka
Summary: The interactions between vesicle and substrate were investigated using simulation and experiment. Polyacrylic acid brushes with cysteine side chains were grafted onto planar lipid membranes. The addition of Cd2+ ions compacted the polymer brushes and influenced the adhesion of lipid vesicles. Wetting of the vesicles occurred at [CdCl2] = 0.25 mM. The shape and adhesion of vesicles were quantitatively evaluated, and simulations revealed that wetting sensitivity was dependent on the interaction range.
Article
Polymer Science
Niklas Blagojevic, Marcus Mueller
Summary: Using a particle-based model, a free-energy functional, and a lattice model, this study investigates the structure and motion of a grain boundary between two orthogonal grains in asymmetric block copolymers. The study reveals insights into transitions and correlations in space and time. By characterizing the system using a free-energy functional and calculating the minimum free-energy path, the study identifies a minimal set of transitions. The results are used to parametrize a lattice model and investigate grain-boundary motion by kinetic Monte Carlo simulation.
