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Publications 2019

Shear Modulus of an Irreversible Diblock Copolymer Network from Self-Consistent Field Theory
Shuanhu Qi, Jiajia Zhou, Friederike Schmid
Macromolecules 52 (24), 9569-9577 (2019);
doi:10.1021/acs.macromol.9b01985

Using self-consistentfield theory, we investigate thestretching-induced microphase separation in an irreversibly cross-linkedpolymer network composed of diblock copolymer chains and estimate itsshear modulus. The topology of the network isfixed to a planar square lattice.The monomer density, the distribution of cross-links, and the free energy ofthe system are calculated. Wefind that the system develops circular domainsat equilibrium, which may merge to lamellae upon compression or stretching.The lamellae are oriented perpendicular to the stretching direction. Cross-links are localized, but their distribution may be anisotropic. For asymmetricstrands, the distributions of different type of cross-links differ from eachother, indicating that the cross-linkfluctuations are inhomogeneous. Thestress is evaluated from the derivative of the free energy of stretched systemswith respect to the deformation in the stretching direction. Using theelasticity theory of isotropic solids allows us to estimate the shear modulus.Wefind that the shear modulus increases if the networkfluctuations are inhomogeneous. Ourfindings may provide guidance forthe design of stiffer soft matter materials.

Order–Order Phase Transitions Induced by Supercritical Carbon Dioxide in Triblock Copolymer Thin Films
Anabella A. Abate, Giang Thi Vu, Cristian M. Piqueras, María Cecilia del Barrio, Leopoldo R. Gómez, Gabriel Catalini, Friederike Schmid, Daniel A. Vega
Macromolecules 52 (20), 7786-7797 (2019);
doi:10.1021/acs.macromol.9b01278

We study the influence of supercritical carbon dioxide(scCO2) on the phase behavior of a cylinder-forming polystyrene-block-polybutadiene-b-polystyrene triblock copolymer thinfilm. Solventannealing with scCO2can produce patterns with long-range order butthese structures become unstable for thinfilms with small thicknesses.These results are in good agreement with self-consistent meanfieldcalculations, which indicate that a drying transition occurs forthicknesses below the radius of gyration of the molecule. Afterdecompression and solvent extraction, the initially swollen polymernanostructure suffers a strong reduction in the average domain spacing, which has a deleterious effect on the degree of order inthe resulting pattern. Both, experiments and Cahn−Hilliard simulations suggest that during decompression the pattern suffersan order−order instability where the collapse of the lattice constant leads to uncommon patterns with long-range orientationalorder but structural distortions at small-length scales.

Influence of Polymer Bidispersity on the Effective Particle–Particle Interactions in Polymer Nanocomposites
Gianmarco Munaò, Antonio De Nicola, Florian Müller-Plathe, Toshihiro Kawakatsu, Andreas Kalogirou, Giuseppe Milano
Macromolecules, (2019);
doi:10.1021/acs.macromol.9b01367

Surface of Half-Neutralized Diamine Triflate Ionic Liquids. A Molecular Dynamics Study of Structure, Thermodynamics, and Kinetics of Water Absorption and Evaporation
N. C. Forero-Martinez, R. Cortes-Huerto, J. F. Mora Cardozo, P. Ballone
The Journal of Physical Chemistry B 123 (40), 8457-8471 (2019);
doi:10.1021/acs.jpcb.9b06619

Steering a solute between coexisting solvation states: Revisiting nonequilibrium work relations and the calculation of free energy differences
Maziar Heidari, Robinson Cortes-Huerto, Raffaello Potestio, Kurt Kremer
The Journal of Chemical Physics 151 (14), 144105 (2019);
doi:10.1063/1.5117780

On the relevance of electrostatic interactions for the structural relaxation of ionic liquids: A molecular dynamics simulation study
Tamisra Pal, Michael Vogel
The Journal of Chemical Physics 150 (12), 124501 (2019);
doi:10.1063/1.5085508

A note on the uniqueness result for the inverse Henderson problem
F. Frommer, M. Hanke, S. Jansen
Journal of Mathematical Physics 60 (9), 093303 (2019);
Highlighted on Scilight, see https://aip.scitation.org/doi/10.1063/1.5134789
doi:10.1063/1.5112137

The inverse Henderson problem of statistical mechanics is the theoretical foundation for many bottom-up coarse-graining techniques for the numerical simulation of complex soft matter physics. This inverse problem concerns classical particles in continuous space which interact according to a pair potential depending on the distance of the particles. Roughly stated, it asks for the interaction potential given the equilibrium pair correlation function of the system. In 1974 Henderson proved that this potential is uniquely determined in a canonical ensemble and he claimed the same result for the thermodynamical limit of the physical system. Here we provide a rigorous proof of a slightly more general version of the latter statement using Georgii's variant of the Gibbs variational principle.

Mechanical and Structural Tuning of Reversible Hydrogen Bonding in Interlocked Calixarene Nanocapsules
Stefan Jaschonek, Ken Schäfer, Gregor Diezemann
The Journal of Physical Chemistry B 123 (22), 4688-4694 (2019);
doi:10.1021/acs.jpcb.9b02676

Temperature dependent mechanical unfolding of calixarene nanocapsules studied by molecular dynamics simulations
Takashi Kato, Ken Schäfer, Stefan Jaschonek, Jürgen Gauss, Gregor Diezemann
The Journal of Chemical Physics 151 (4), 045102 (2019);
doi:10.1063/1.5111717

Relative entropy indicates an ideal concentration for structure-based coarse graining of binary mixtures
David Rosenberger and Nico F. A. van der Vegt
Phys. Rev. E 99, 053308 (2019);
doi:10.1103/PhysRevE.99.053308

Transferability of Local Density-Assisted Implicit Solvation Models for Homogeneous Fluid Mixtures
David Rosenberger, Tanmoy Sanyal, M. Scott Shell, and Nico F. A. van der Vegt
J. Chem. Theory Comp 15, 2881-2895 (2019);
doi:10.1021/acs.jctc.8b01170

Conditional reversible work coarse-grained models with explicit electrostatics - An application to butylmethylimidazolium ionic liquids
Gregor Deichmann and Nico F. A. van der Vegt
J. Chem. Theory Comp. 15, 1187-1198 (2019);
doi:10.1021/acs.jctc.8b00881

Phase equilibria modeling with systematically coarse-grained models - A comparative study on state point transferability
Gregor Deichmann, Marco Dallavalle, David Rosenberger and Nico F. A. van der Vegt
J. Phys. Chem. B 123, 504-515 (2019);
doi:10.1021/acs.jpcb.8b07320

Polydispersity Effects on Interpenetration in Compressed Brushes
Leonid I. Klushin, Alexander M. Skvortsov, Shuanhu Qi, Torsten Kreer, Friederike Schmid
Macromolecules 52 (4), 1810-1820 (2019);
doi:10.1021/acs.macromol.8b02361

How ill-defined constituents produce well-defined nanoparticles: Effect of polymer dispersity on the uniformity of copolymeric micelles
Sriteja Mantha, Shuanhu Qi, Matthias Barz, Friederike Schmid
Physical Review Materials 3 (2), (2019);
doi:10.1103/physrevmaterials.3.026002

An asymptotic preserving scheme for kinetic chemotaxis models in two space dimensions
A. Chertock, A. Kurganov, M. Lukacova-Medvidova, S. Nur Oezcan
Kinetic and Related Models 12 (1), 195–216 (2019);
URL: http://aimsciences.org//article/doi/10.3934/krm.2019009
doi:10.3934/krm.2019009

In this paper, we study two-dimensional multiscale chemotaxis models based on a combination of the macroscopic evolution equation for chemoattractant and microscopic models for cell evolution. The latter is governed by a Boltzmann-type kinetic equation with a local turning kernel operator which describes the velocity change of the cells. The parabolic scaling yields a non-dimensional kinetic model with a small parameter, which represents the mean free path of the cells. We propose a new asymptotic preserving numerical scheme that reflects the convergence of the studied micro-macro model to its macroscopic counterpart-the Patlak-Keller-Segel system-in the singular limit. The method is based on the operator splitting strategy and a suitable combination of the higher-order implicit and explicit time discretizations. In particular, we use the so-called even-odd decoupling and approximate the stiff terms arising in the singular limit implicitly. We prove that the resulting scheme satisfies the asymptotic preserving property. More precisely, it yields a consistent approximation of the Patlak-Keller-Segel system as the mean-free path tends to 0. The derived asymptotic preserving method is used to get better insight to the blowup behavior of two-dimensional kinetic chemotaxis model.

Energy-stable linear schemes for polymer-solvent phase field models
P. Strasser, G. Tierra, B. Dünweg, M. Lukacova-Medvidova
Comp. Math. Appl. 77 (1), 125-143 (2019);
URL: https://www.sciencedirect.com/science/article/pii/S0898122118305303?via%3Dihub
doi:https://doi.org/10.1016/j.camwa.2018.09.018

We present new linear energy-stable numerical schemes for numerical simulation of complex polymer–solvent mixtures. The mathematical model proposed by Zhou et al. (2006) consists of the Cahn–Hilliard equation which describes dynamics of the interface that separates polymer and solvent and the Oldroyd-B equations for the hydrodynamics of polymeric mixtures. The model is thermodynamically consistent and dissipates free energy. Our main goal in this paper is to derive numerical schemes for the polymer–solvent mixture model that are energy dissipative and efficient in time. To this end we will propose several problem-suited time discretizations yielding linear schemes and discuss their properties.

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