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Charles M. Schroeder - One of the best experts on this subject based on the ideXlab platform.

  • Single Polymer Dynamics for Molecular Rheology
    Journal of Rheology, 2018
    Co-Authors: Charles M. Schroeder
    Abstract:

    Single Polymer Dynamics offers a powerful approach to study molecular-level interactions and dynamic microstructure in materials. Direct visualization of single chain Dynamics has uncovered new ideas regarding the rheology and non-equilibrium Dynamics of macromolecules, including the importance of molecular individualism, dynamic heterogeneity, and molecular sub-populations that govern macroscale behavior. In recent years, the field of single Polymer Dynamics has been extended to increasingly complex materials, including architecturally complex Polymers such as combs, bottlebrushes, and ring Polymers and entangled solutions of long chain Polymers in flow. Single molecule visualization, complemented by modeling and simulation techniques such as Brownian Dynamics and Monte Carlo methods, allow for unparalleled access to the molecular-scale Dynamics of Polymeric materials. In this review, recent progress in the field of single Polymer Dynamics is examined by highlighting major developments and new physics to emerge from these techniques. The molecular properties of DNA as a model Polymer are examined, including the role of flexibility, excluded volume interactions, and hydrodynamic interactions in governing behavior. Recent developments in studying Polymer Dynamics in time-dependent flows, new chemistries and new molecular topologies, and the role of intermolecular interactions in concentrated solutions are considered. Moreover, cutting-edge methods in simulation techniques are further reviewed as an ideal complementary method to single Polymer experiments. Future work aimed at extending the field of single Polymer Dynamics to new materials promises to uncover original and unexpected information regarding the flow Dynamics of Polymeric systems.

  • Single Polymer Dynamics of topologically complex DNA
    Current Opinion in Colloid & Interface Science, 2016
    Co-Authors: Danielle J. Mai, Charles M. Schroeder
    Abstract:

    Abstract Single molecule studies allow for the direct observation of Polymer Dynamics in dilute and concentrated solutions, thereby revealing Polymer chain conformations and molecular sub-populations that may be obscured in ensemble-level measurements. Over the past two decades, researchers have used DNA as a model system to study Polymer Dynamics at the molecular level. The vast majority of studies have focused on linear DNA molecules; however, researchers have recently begun to study Polymers with complex topologies and architectures at the single molecule level. Here, we explore recent work in single Polymer Dynamics focused on topologically complex DNA, including knots, ring Polymers, and branched Polymers. Experimental, computational, and theoretical advances have enabled in-depth studies of topologically complex DNA, with recent efforts focused on complex molecular conformations, intermolecular interactions, and topology-dependent Dynamics. In this article, we highlight recent work aimed at understanding the interplay between molecular-scale behavior and the emergent properties of Polymeric materials.

  • Determining elasticity from single Polymer Dynamics
    Soft matter, 2014
    Co-Authors: Folarin Latinwo, Charles M. Schroeder
    Abstract:

    The ability to determine Polymer elasticity and force-extension relations from Polymer Dynamics in flow has been challenging, mainly due to difficulties in relating equilibrium properties such as free energy to far-from-equilibrium processes. In this work, we determine Polymer elasticity from the dynamic properties of Polymer chains in fluid flow using recent advances in statistical mechanics. In this way, we obtain the force-extension relation for DNA from single molecule measurements of Polymer Dynamics in flow without the need for optical tweezers or bead tethers. We further employ simulations to demonstrate the practicality and applicability of this approach to the Dynamics of complex fluids. We investigate the effects of flow type on this analysis method, and we develop scaling laws to relate the work relation to bulk Polymer viscometric functions. Taken together, our results show that nonequilibrium work relations can play a key role in the analysis of soft material Dynamics.

  • Model systems for single molecule Polymer Dynamics
    Soft matter, 2011
    Co-Authors: Folarin Latinwo, Charles M. Schroeder
    Abstract:

    Double stranded DNA (dsDNA) has long served as a model system for single molecule Polymer Dynamics. However, dsDNA is a semiflexible Polymer, and the structural rigidity of the DNA double helix gives rise to local molecular properties and chain Dynamics that differ from flexible chains, including synthetic organic Polymers. Recently, we developed single stranded DNA (ssDNA) as a new model system for single molecule studies of flexible Polymer chains. In this work, we discuss model Polymer systems in the context of “ideal” and “real” chain behavior considering thermal blobs, tension blobs, hydrodynamic drag and force–extension relations. In addition, we present monomer aspect ratio as a key parameter describing chain conformation and Dynamics, and we derive dynamical scaling relations in terms of this molecular-level parameter. We show that asymmetric Kuhn segments can suppress monomer–monomer interactions, thereby altering global chain Dynamics. Finally, we discuss ssDNA in the context of a new model system for single molecule Polymer Dynamics. Overall, we anticipate that future single Polymer studies of flexible chains will reveal new insight into the dynamic behavior of “real” Polymers, which will highlight the importance of molecular individualism and the prevalence of non-linear phenomena.

Marcus Muller - One of the best experts on this subject based on the ideXlab platform.

  • translationally invariant slip spring model for entangled Polymer Dynamics
    Physical Review Letters, 2012
    Co-Authors: Veronica C Chappa, David C Morse, Annette Zippelius, Marcus Muller
    Abstract:

    The topological effect of noncrossability of long flexible macromolecules is effectively described by a slip-spring model, which represents entanglements by local, pairwise, translationally invariant interactions that do not alter any equilibrium properties. We demonstrate that the model correctly describes many aspects of the dynamical and rheological behavior of entangled Polymer liquids, such as segmental mean-square displacements and shear thinning, in a computationally efficient manner. Furthermore, the model can account for the reduction of entanglements under shear.

Yuichi Masubuchi - One of the best experts on this subject based on the ideXlab platform.

  • Multi-chain Slip-spring Model for Entangled Polymer Dynamics
    The Journal of chemical physics, 2012
    Co-Authors: Takashi Uneyama, Yuichi Masubuchi
    Abstract:

    It has been established that entangled Polymer Dynamics can be reasonably described by single chain models such as tube and slip-link models. Although the entanglement effect is a result of hard-core interaction between chains, linkage between the single chain models and the real multi-chain system has not been established yet. In this study, we propose a multi-chain slip-spring model where bead-spring chains are dispersed in space and connected by slip-springs inspired by the single chain slip-spring model [A. E. Likhtman, Macromolecules 38, 6128 (2005)]. In this model the entanglement effect is replaced by the slip-springs, not by the hard-core interaction between beads so that this model is located in the niche between conventional multi-chain simulations and single chain models. The set of state variables are the position of beads and the connectivity (indices) of the slip-springs between beads. The Dynamics of the system is described by the time evolution equation and stochastic transition Dynamics for these variables. We propose a simple model which is based on the well-defined total free-energy and detailed balance condition. The free energy in our model contains a repulsive interaction between beads, which compensate the attractive interaction artificially generated by the slip-springs. The explicit expression of linear relaxation modulus is also derived by the linear response theory. We also propose a possible numerical scheme to perform simulations. Simulations reproduced expected bead number dependence in transitional regime between Rouse and entangled Dynamics for the chain structure, the central bead diffusion, and the linear relaxation modulus.

  • Molecular Simulations for Entangled Polymer Dynamics
    Nihon Reoroji Gakkaishi, 2006
    Co-Authors: Yuichi Masubuchi
    Abstract:

    A novel method for multi-body molecular simulations for entangled Polymers including branch Polymers, Polymer blends and coPolymers is developed in this study. Entangled Polymer Dynamics is important in industry and still challengeable in Polymer science due to complicated rheology caused by a broad variety of controllable Polymer architectures such as molecular weight, molecular weight distribution, long chain branching, coPolymerization, etc. and freedom of their blends. Conventional molecular simulations are inadequate to the Polymer Dynamics in long time range because of huge calculation cost. Theoretical approaches based on reptation theories are essentially difficult for multi-component situations due to the self-consistent treatment of entanglement among many chains. In this study a new method of molecular simulations for entangled Polymer Dynamics is developed based on the primitive chain network model where Polymers are considered as primitive chains forming real network in 3D space similarly to the conventional molecular simulations and distinguishably from other entanglement based models. Reasonable consistency on established scaling behaviors for static and dynamic properties and quantitative agreement with experiments for linear and nonlinear rheology have been confirmed for linear and branched Polymers. For coPolymers and blends reasonable results have been obtained on phase behaviors.

J. M. J. Van Leeuwen - One of the best experts on this subject based on the ideXlab platform.

  • Semiflexible Polymer Dynamics with a bead-spring model
    Journal of Statistical Mechanics: Theory and Experiment, 2014
    Co-Authors: Gerard T. Barkema, Debabrata Panja, J. M. J. Van Leeuwen
    Abstract:

    We study the dynamical properties of semiflexible Polymers with a recently introduced bead-spring model. We focus on double-stranded DNA. The two parameters of the model, $T^*$ and $\nu$, are chosen to match its experimental force-extension curve. The bead-spring Hamiltonian is approximated in the first order by the Hessian that is quadratic in the bead positions. The eigenmodels of the Hessian provide the longitudinal (stretching) and transverse (bending) eigenmodes of the Polymer, and the corresponding eigenvalues match well with the established phenomenology of semiflexible Polymers. Using the longitudinal and transverse eigenmodes, we obtain analytical expressions of (i) the autocorrelation function of the end-to-end vector, (ii) the autocorrelation function of a bond (i.e., a spring, or a tangent) vector at the middle of the chain, and (iii) the mean-square displacement of a tagged bead in the middle of the chain, as sum over the contributions from the modes. We also perform simulations with the full Dynamics of the model. The simulations yield numerical values of the correlation functions (i-iii) that agree very well with the analytical expressions for the linearized Dynamics. We also study the mean-square displacement of the longitudinal component of the end-to-end vector that showcases strong nonlinear effects in the Polymer Dynamics, and we identify at least an effective $t^{7/8}$ power-law regime in its time-dependence. Nevertheless, in comparison to the full mean-square displacement of the end-to-end vector the nonlinear effects remain small at all times --- it is in this sense we state that our results demonstrate that the linearized Dynamics suffices for dsDNA fragments that are shorter than or comparable to the persistence length. Our results are consistent with those of the wormlike chain (WLC) model, the commonly used descriptive tool of semiflexible Polymers.

Veronica C Chappa - One of the best experts on this subject based on the ideXlab platform.

  • translationally invariant slip spring model for entangled Polymer Dynamics
    Physical Review Letters, 2012
    Co-Authors: Veronica C Chappa, David C Morse, Annette Zippelius, Marcus Muller
    Abstract:

    The topological effect of noncrossability of long flexible macromolecules is effectively described by a slip-spring model, which represents entanglements by local, pairwise, translationally invariant interactions that do not alter any equilibrium properties. We demonstrate that the model correctly describes many aspects of the dynamical and rheological behavior of entangled Polymer liquids, such as segmental mean-square displacements and shear thinning, in a computationally efficient manner. Furthermore, the model can account for the reduction of entanglements under shear.