Next CASA Minisymposium Wednesday
January 11, 2017
Simulation Approaches in Soft Matter
09.45 - 13:00
Dr. Markus Huetter
10:00 - 10:45
Minimalist two-scale model
for the viscoelastic behavior of elastomers
filled with hard nano-particles
(1,2), Didier Long (3), Markus
Huetter (1, *)
(1) Eindhoven University of Technology,
Polymer Technology, Department of Mechanical
Box 513, 5600 MB Eindhoven, The Netherlands.
(2) Dutch Polymer Institute (DPI), P.O. Box 902,
5600 AX Eindhoven, The Netherlands.
(3) Laboratory `Polymeres et Materiaux Avances',
Unite Mixte de Recherche CNRS/Solvay, France.
A dynamic two-scale model is presented for
describing the mechanical behavior of elastomers
filled with hard nanoparticles, particularly the
Payne effect and the Mullins effect. According to
literature, both of these effects have their
origin in the constraint-induced vitrification of
the matrix material between neighboring filler
particles, leading to so-called glassy bridges.
Yielding of the latter amounts to the Payne
effect, while physical aging of the glassy
material gives rise to the Mullins effect.
Many-particle models have been developed to
describe the mechanical behavior of such
composites [Merabia et al., Macromolecules 41,
8252-8266 (2008); Merabia et al., J. Polym. Sci.
Pol. Phys. 48, 1495-1508 (2010); Papon et al.,
Macromolecules 45, 2891-2904 (2012)]. For
computational efficiency and in view of
macroscopically inhomogeneous deformations, we
strive in this contribution to reduce the model
complexity drastically, while keeping the
essential physics in the model. Using
nonequilibrium thermodynamics, we propose a
dynamic two-scale model that couples continuum
mechanics with the dynamics of a single
representative particle-pair on the meso-scale.
This reduced model is studied numerically in
oscillatory deformation. The resulting
stress-strain response (Payne effect) is compared
to the many-particle model in the literature, and
benefits as well as short-comings of the new
approach are discussed. Finally, it is discussed
how the physical aging of the glassy bridges
(Mullins effect) can be incorporated, using the
concept of kinetic/vibrational and conformational
subsystems, akin to two-temperature models in the
This research was funded by the European Union
through the project COMPNANOCOMP under Grant
Number 295355, and forms part of the research
programme of the Dutch Polymer Institute (DPI),
project EU-FP-001 COMPNANOCOMP.
Martin Mueser (Universitaet des Saarlandes)
11:00 - 11:45
Modeling dielectric response
functions and non-equilibrium redox reactions
with charge transfer potentials
A central problem
in the modeling of materials at the atomic scale
is the simulation of non-equilibrium phenomena
involving charge transfer. An important example is
the fundamental difficulty to describe the
processes occurring during the discharge or the
recharging of a Galvanic cell. Most methods,
including DFT and conventional
charge-equilibration methods, fail because they
(must) assume the chemical potential to be
constant at the beginning of the simulation. Such
minimizations automatically annihilate all voltage
in a full (nanoscale) Galvanic model cell.
In my talk, I present the split-charge
equilibration method, which allows one to describe
non-equilibrium redox reactions in force-field
based simulations. This in turn enables one to
simulate from atomistic principles the generic
processes that occur during the discharge and the
recharge of a Galvanic cell. An interesting side
aspect of the splitcharge method is that it can
also be used to describe the dielectric response
function of continuous media on coarse scales.
This makes it a promising candidate for the
multi-scale modeling of dielectric phenomena.
Prof. Dr. Kurt
Kremer (Max Planck Institute for Polymer
12:00 - 12:45
Co(non)solvency or the
puzzle of polymer properties in mixed good or
relation between atomistic structure,
architecture, molecular weight
and material properties is of basic concern
of modern soft matter science. Here
computer simulations on different levels of
resolution play an increasingly
important role. To progress further adaptive
schemes are being developed, which
allow for a free exchange of particles
(atoms, molecules) between the different
levels of resolution. Typical examples
include the solvation of polymers in
mixed solvents, especially PNIPAM and PMMA
in water alcohol mixtures. The first
reveals an interesting coil-globule-coil
transition. This conformational
transition cannot be explained within the
classical Flory-Huggins picture,
which is the standard mean field theory for
polymer solutions and mixtures. The
results point towards a general design of
'smart stimuli responsive polymers'.
The second displays a weak swelling in a
mixture of two poor solvents.
This work has been
performed in collaboration
with D. Mukherji and C. Marques.
Mukherji and K. Kremer Macrom. 46, 9158 (2013) D. Mukherji, C. M. Marques, K. Kremer,
Nat. Comm. 5, 4882 (2014) D. Mukherji, C. M. Marques, T.
Stuehn, K. Kremer, J. Chem. Phys. 142,
D. Mukherji, M. Wagner, M. D. Watson, S.
Winzen, T. E. de Oliveira, C. M.
Marques, K. Kremer, Soft Matter 12, 7995?8003