Multiscale modeling of polymers at interfaces

Varnik, Fathollah; Binder, Kurt

doi:10.3139/146.110209

Cited by 22 publications

(25 citation statements)

References 134 publications

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“…They are not only interesting from a fundamental point of view but also play a major role in various applications such as in lubricants, surface coatings, and composite materials, where these macromolecules can control the overall performance of the system (1,2). general reason they are not fully understood, which makes the experimental data analysis difficult (4). To discover the range of surface effects on the melt and their origins, which are not well understood, Molecular Dynamics (MD) simulation studies can play a major role.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamic Study of the Structure and Dynamics of Polymer Melt at Solid Surfaces

et al. 2014

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We investigate the dynamic and static properties of a polymer melt near solid surfaces. The melt, composed of linear chains, is confined between two solid walls with one of the walls being repulsive; whereas the opposite, attractive wall, is characterized by different degrees of roughness, caused by an array of short perpendicular pillars with variable grafting density. We demonstrate the remarkable fact that the conformations of chains in the melt at the interfaces are mostly unaffected by the strength of substrate/polymer attraction. Moreover, they practically coincide with the conformations of a single end-grafted chain at the critical point of adsorption, in agreement with Silberberg's hypothesis. This agreement is corroborated by the analysis of the size distributions of trains, loops, and tails of melt chains at the walls that are found to be perfectly described by analytical expressions pertaining to end-grafted single chains at critical adsorption. The adsorbed amount at the attractive bottom surface is found to scale with macromolecule length as ∝ √ N regardless of adsorption strength. We also find that the pressure of the melt P N decreases as P N − P ∞ ∝ N −1 (where P ∞ is the extrapolated pressure for N → ∞) with growing length N of the chains whereas the surface tension γ at both walls is found to decline as γ N ∝ N −2/3 . Eventually, a study of the polymer dynamics at the rough interface reveals that surface roughness leads to dramatic drop of the coefficient for lateral diffusion whenever the separation between obstacles (neighboring pillars) becomes less than ≈ 2R g where R g is the unperturbed radius of gyration of chains in the bulk.

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Section: Introductionmentioning

confidence: 99%

Molecular Dynamic Study of the Structure and Dynamics of Polymer Melt at Solid Surfaces

et al. 2014

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“…The relation between the dynamics of structural rearrangement and response in driven amorphous materials has been subject of growing interest in the past decade [1][2][3][4][5][6]. A central issue in this context is the growth of spatial correlations upon approaching the glass transition (see, e.g., [7][8][9][10][11][12] and references therein). In quiescent glasses, it is well established that upon approaching the glass transition, dynamic correlations grow; this is manifested in an increase of the dynamic susceptibility [13] as well as strongly non-Gaussian displacement distributions.…”

Section: Introductionmentioning

confidence: 99%

Single-particle fluctuations and directional correlations in driven hard-sphere glasses

et al. 2013

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Single-particle fluctuations and directional correlations in driven hard-sphere glassesMandal, S.; Chikkadi, V.; Nienhuis, B.; Raabe, R.; Schall, P.; Varnik, F. Published in:Physical Review E DOI:10.1103/PhysRevE.88.022129 Link to publication Citation for published version (APA):Mandal, S., Chikkadi, V., Nienhuis, B., Raabe, R., Schall, P., & Varnik, F. (2013). Single-particle fluctuations and directional correlations in driven hard-sphere glasses. Physical Review E, 88, 022129. DOI: 10.1103/PhysRevE.88.022129 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Via event-driven molecular dynamics simulations and experiments, we study the packing-fraction and shearrate dependence of single-particle fluctuations and dynamic correlations in hard-sphere glasses under shear. At packing fractions above the glass transition, correlations increase as shear rate decreases: the exponential tail in the distribution of single-particle jumps broadens and dynamic four-point correlations increase. Interestingly, however, upon decreasing the packing fraction, a broadening of the exponential tail is also observed, while dynamic heterogeneity is shown to decrease. An explanation for this behavior is proposed in terms of a competition between shear and thermal fluctuations. Building upon our previous studies [Chikkadi et al., Europhys. Lett. 100, 56001 (2012)], we further address the issue of anisotropy of the dynamic correlations.

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“…3 We represent the surfaces by perfectly crystalline walls rather than continuous perfectly smooth surfaces as the latter is known to increase the diffusive dynamics of the polymers near the walls. 21 Each CG wall bead possesses the mass of a PS monomer (104.06 amu). Each surface is composed of two sheets of 1368 beads arranged on a hexagonal lattice.…”

Section: Coarse-grained Force Field Parameterization Of Polystyrene Smentioning

confidence: 99%

Modeling of Polystyrene under Confinement: Exploring the Limits of Iterative Boltzmann Inversion

Bayramoglu

Faller

2013

Macromolecules

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ABSTRACT:We explore the limits of a purely structure based coarse-graining technique, the iterative Boltzmann inversion (IBI), in the coarse-graining of a confined concentrated polystyrene solution. In the first place, some technical considerations and challenges encountered in the course of the optimization process are represented. The concepts of the choice of the initial potentials and the cross-dependency of the interactions as well as the order of optimization are discussed in detail. Furthermore, the transferability of a previously developed CG confined polystyrene solution model, the "parent CG confined model", to different degrees of confinement at constant concentration and temperature is examined. We investigate if a CG force field developed for a confined polymer solution by IBI is sensitive to changes in the degree of localization or arrangement of polymers near the surfaces although the concentration is kept constant. For this purpose, reference atomistic simulations on systems of different confinement levels have been performed. The differences in the structure and dynamics of the chains are addressed. Results are compared with those of an unconfined (bulk) system at the same concentration. The chain dimensions and orientations as a function of the distance from the surfaces are also reported. To the best of our knowledge, this is the first computational study that investigates the structural behavior of polymers in close proximity of the surfaces in a concentrated polymer solution rather than in a melt. Transferability of the parent CG confined model is tested by employing the parent force field in CG simulations of the reference systems. Results indicate that the degree of arrangement of monomers and solvent molecules near the surfaces is an important factor that needs to be paid attention to when considering the application of a CG force field developed by IBI to different degrees of confinement.

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Multiscale modeling of polymers at interfaces

Cited by 22 publications

References 134 publications

Molecular Dynamic Study of the Structure and Dynamics of Polymer Melt at Solid Surfaces

Molecular Dynamic Study of the Structure and Dynamics of Polymer Melt at Solid Surfaces

Single-particle fluctuations and directional correlations in driven hard-sphere glasses

Modeling of Polystyrene under Confinement: Exploring the Limits of Iterative Boltzmann Inversion

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