Article
Polymer Science
Shifeng Nian, Baiqiang Huang, Guillaume Freychet, Mikhail Zhernenkov, Li-Heng Cai
Summary: Bottlebrush molecules are branched polymers with a densely grafted linear backbone. Contrary to existing understanding, the interbackbone distance in bottlebrush polymers increases as the grafting density of side chains decreases. This discovery provides a paradigm-shifting understanding of the molecular structure of bottlebrush polymers.
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
Chia-Cheng Chu, Pai-Yi Hsiao
Summary: This article proposes a two-stage model to explain the phenomena of chain expansion released from a confining cavity. In the first stage, the chain is assumed to expand as a sphere, while in the second stage it expands like a coil. The kinetic equations for the variation of chain size are derived in the two stages by balancing the rate of the free energy change with the rate of energy dissipation. Langevin dynamics simulations are performed to examine the theory. The simulation results support the theory and reveal that the expansion process is dominated by the second stage, confirming the predicted curve for coil expansion.
Article
Materials Science, Multidisciplinary
Haoxiang Li, Ruibin Ma, Wenfeng Zhang, Shikai Hu, Xiuying Zhao, Liqun Zhang, Yangyang Gao
Summary: The transient behavior of structure and stress response to the shear strain in polymer nanocomposites (PNCs) is investigated using nonequilibrium molecular dynamics (NEMD) simulation. The stress overshoot behavior is observed in both polymer matrix and nanoparticles (NPs). The extent of the stress overshoot remains nearly unchanged with increasing the NPs loading while it rises with improving the shear rate or polymer-NP interaction.
MATERIALS TODAY 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
Polymer Science
Haoxiang Li, Haoyu Wu, Wenfeng Zhang, Xiuying Zhao, Liqun Zhang, Yangyang Gao
Summary: This study investigates the rheological properties of polymer nanocomposites using reverse nonequilibrium molecular dynamics simulation, and finds that shear rate has a significant impact on shear viscosity and chain extension. The increase in volume fraction of nanoparticles and polymer-NP interaction leads to a higher zero-shear viscosity, attributed to the formation of network structures causing delayed dynamics. Additionally, both the first and second normal stress differences exhibit power laws with shear rate.
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
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
Chemistry, Physical
Abdullah O. Hamza, Francesco N. Viscomi, Jean-Sebastien G. Bouillard, Ali M. Adawi
Summary: This study investigates the relationship between FRET rate and the local density of optical states, demonstrating through both experimental and theoretical methods its linear dependence on LDOS. By controlling the size of silver nanoparticles, the FRET rate in systems can be directly manipulated, offering a simple yet powerful method for controlling FRET rate.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Polymer Science
Junrou Huang, Nabil Ramlawi, Grant S. Sheridan, Chen Chen, Randy H. Ewoldt, Paul V. Braun, Christopher M. Evans
Summary: Polymer membranes are commonly used in passive separations with lower energy consumption compared to distillation. Glassy materials are usually chosen for gas separations due to their sensitivity to size differences, while rubbers are used for liquid separations due to solubility differences. In this study, vitrimers (dynamic polymer networks with associative bond exchange) were synthesized with boronic ester crosslinks and different dynamic bond densities, and the diffusion of a large aromatic dye was measured. The results showed that the dynamic bond exchange, accelerated by neighboring nitrogen groups, enhanced penetrant transport by more than 1 order of magnitude. These findings provide a general route for designing polymer membranes with selectivity through dense crosslinking and dynamic covalent chemistry.
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
Chemistry, Physical
Andrey Milchev, Peicho Petkov
Summary: The structure and scaling properties of inwardly curved polymer brushes tethered to the inner surface of spherical shells were studied using molecular dynamics simulations. The results were compared with theoretical predictions and examined various structural properties, such as density profiles and brush thickness. The findings also revealed a new scaling relationship between the local pressure and grafting density.
JOURNAL OF CHEMICAL PHYSICS
(2023)
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
Physics, Multidisciplinary
Da Wang, Tonnishtha Dasgupta, Ernest B. van der Wee, Daniele Zanaga, Thomas Altantzis, Yaoting Wu, Gabriele M. Coli, Christopher B. Murray, Sara Bals, Marjolein Dijkstra, Alfons van Blaaderen
Summary: The influence of geometry on the local and global packing of particles is crucial, with binary mixtures of hard-sphere-like nanoparticles crystallizing into icosahedral clusters in bulk. The local structure of a significant portion of particles is similar to the MgCu(2)Laves phase, which has potential applications in photonics. The nucleation of icosahedral clusters is observed away from the spherical boundary, providing new insights into particle-level studies of binary crystallization.
Article
Chemistry, Physical
Entao Yang, James F. Pressly, Bharath Natarajan, Robert Colby, Karen I. Winey, Robert A. Riggleman
Summary: This study examines the dynamics in polymer nanocomposites (PNCs) and quantitatively separates the role of polymer packing from other effects on the dynamics near the nanoparticle surfaces. The results show that the slow interfacial dynamics in PNCs is not solely due to polymer packing differences, but also the change of structure-dynamics relationships. The study also demonstrates how the decomposition of dynamics can accurately predict strain-time creep curves for PNCs from their static configuration, providing insights into the effects of polymer-nanoparticle interfaces on creep suppression in PNCs.
Article
Physics, Multidisciplinary
Gerardo Campos-Villalobos, Marjolein Dijkstra, Alessandro Patti
Summary: By using computer simulations, this study investigates the phase behavior of hard-core spherocylinders coated by a soft deformable corona. The competition between different length scales results in the stabilization of unconventional in-plane lattices, including hexagonal, square, high-density hexagonal crystals, and a dodecagonal quasicrystal. This research opens up new opportunities for controlling the assembly of anisotropic nanoparticles to achieve structures with preengineered symmetry-dependent physical properties.
PHYSICAL REVIEW LETTERS
(2021)
Article
Polymer Science
J. Javier Burgos-Marmol, Alessandro Patti
Summary: The study shows that accurate tuning of interactions between Janus nanodimers (NDs) and copolymer blocks can lead to precise control over the distribution and orientation of NDs in the polymer matrix. NDs are typically found within the lamellae when enthalpy-driven forces offset their entropic counterparts, whereas excluded-volume effects primarily drive the distribution of NDs in the inter-lamellar spacing when enthalpy-driven forces are not significant. Affinity between host and guest species plays a key role in determining the distribution and orientation of NDs within the polymer matrix, ultimately influencing their ability to diffuse through the matrix.
Article
Chemistry, Physical
Luca Tonti, Fabian A. Garcia Daza, Alessandro Patti
Summary: The diffusion of macromolecules in dense colloidal suspensions is significantly affected by the presence of randomly oriented clusters of colloidal cuboids, leading to pronounced non-Gaussian dynamics. The influence of long-range orientational ordering on diffusion and the role of ordered crowding in different phases are carefully studied in this work.
JOURNAL OF MOLECULAR LIQUIDS
(2021)
Article
Mechanics
Effran Mirzad Rafael, Luca Tonti, Daniel Corbett, Alejandro Cuetos, Alessandro Patti
Summary: At the particle scale, a strong correlation was detected between response time and particle anisotropy, with self-dual-shaped cuboids exhibiting surprisingly slow response times during reorientation.
Article
Mechanics
Alessandro Patti, Alejandro Cuetos
Summary: Understanding the behavior of colloidal suspensions in confined environments is crucial for practical applications. By studying how colloids behave in nanopores, it is possible to control their phase behavior and stabilize unique morphologies that cannot form in bulk. The dynamics of colloids in confined environments are significantly influenced by their ability to diffuse in different directions within the nanopores.
Article
Chemistry, Physical
Fabian A. Garcia Daza, Antonio M. Puertas, Alejandro Cuetos, Alessandro Patti
Summary: Understanding the rheology of colloidal suspensions is crucial for formulating industry-relevant products. Microrheology technique allows for the analysis of viscoelastic behavior at a microscopic level. The extended dynamic Monte Carlo technique shows promise in investigating active microrheology in colloidal suspensions.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2022)
Article
Chemistry, Physical
Fabian A. Garcia Daza, Antonio M. Puertas, Alejandro Cuetos, Alessandro Patti
Summary: This study investigates particle tracking in soft materials using Dynamic Monte Carlo simulations and microrheology techniques. The effects of size and ordering on the system relaxation are evaluated under different structural properties. The results reveal that the size of the tracer and the background ordering have a direct influence on the observed microrheology phenomena.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Chemistry, Physical
L. Tonti, F. A. Garcia Daza, A. Patti
Summary: Applying an electric field to polarizable colloidal particles induces the formation of string-like clusters and alters the fluid mechanical and rheological properties. The dynamics of self-assembly and the viscoelastic response of the model fluid under the electric field are investigated using simulations and microrheology.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Alvaro Rodriguez-Rivas, Alessandro Patti, Alejandro Cuetos
Summary: Biaxial nematic (NB) liquid crystals are promising candidates for next-generation displays. Experimental evidence supported by theory and simulation has proven that suitable colloidal particles can form NB fluids. However, there has been less attention given to the study of their transport properties. This study investigates the equilibrium dynamics of field-induced NB phases using Dynamic Monte Carlo simulations, focusing on the diffusion coefficients of monodisperse hard cuboids. The results show that the diffusion of prolate cuboids is significantly faster in biaxial nematics compared to less ordered fluids, but no such increase is observed for oblate cuboids at high packing fractions.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Chemistry, Physical
Justinas Slepavicius, Alessandro Patti, James L. McDonagh, Carlos Avendano
Summary: The ability to predict transport properties of fluids has been a continuous effort in molecular modeling, with different approaches like theoretical, empirical, and semi-empirical correlations being used. Recent attempts have focused on improving the accuracy of predictions using Machine-Learning (ML) methods. This study investigates the application of three ML algorithms to represent transport properties of systems with spherical particles interacting via the Mie potential, and demonstrates the prediction of self-diffusion coefficient for small molecular systems using molecular parameters and experimental data.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Fabian A. Garcia Daza, Antonio M. Puertas, Alejandro Cuetos, Alessandro Patti
Summary: The rheology of colloidal suspensions is important in formulation technology and fundamental science, and microrheology has emerged as a tool to assess materials at the microscopic level. In this study, we used dynamic Monte Carlo simulations to investigate the viscoelasticity of self-assembling smectic liquid crystals using active microrheology. The results show that the mechanical properties are influenced by the size of the particles and the directionality of the external forces.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Physics, Fluids & Plasmas
Effran Mirzad Rafael, Luca Tonti, Fabian A. Garcia Daza, Alessandro Patti
Summary: By conducting dynamic Monte Carlo simulations, the microrheology of isotropic suspensions of hard-core colloidal cuboids is investigated. The local viscoelastic behavior of these fluids is inferred by studying the dynamics of a probe spherical particle that is incorporated in the host phase and dragged by an external force. Different responses are observed by tuning the geometry of cuboids and system density, and are quantified by measuring the effective friction perceived by the probe particle.
Article
Physics, Fluids & Plasmas
Justinas Slepavicius, Carlos Avendano, Breanndan O. Conchuir, Alessandro Patti
Summary: In this study, the dynamics of isotropic fluids of colloidal nanotrimers were investigated using Molecular Dynamics simulation. The existence of slow and fast nanotrimers and the occurrence of non-Gaussianity at intermediate timescales were detected.
Article
Physics, Fluids & Plasmas
Daniela Cywiak, Alejandro Gil-Villegas, Alessandro Patti
Summary: Understanding the relaxation dynamics of colloidal suspensions, especially the impact of long-ranged ordering on the diffusion of soft repulsive rodlike particles, sheds light on the influence of translational and orientational order on the mobility of particles. Temperature plays a critical role in determining the response time of system relaxation and the self-diffusion coefficients of the particles, ultimately affecting the concentration of rods diffusing faster than average.
Article
Physics, Fluids & Plasmas
Francisco Javier Lobo-Cabrera, Alessandro Patti, Fernando Govantes, Alejandro Cuetos
Summary: Microorganisms like bacteria have the ability to form biofilms on surfaces, and the size and concentration of polymer substances can impact biofilm formation and growth. Addition of model polymeric molecules induces particle self-assembly and aggregation, resulting in different colony morphologies. The presence of a threshold polymer concentration determines the mechanism of polymer-induced compaction in bacterial biofilms.