Multiscale Simulation of Polymers near Metal Surfaces

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Multiscale Simulation of Polymers near (Metal)
Surfaces

• K. Kremer
• Max Planck Institute for Polymer Research, Mainz

09/2005
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• Max-Planck Institute for Polymer Research Mainz

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Characteristic Time and Length Scales
Soft fluid
Time
Finite elements
bilayer buckles
Length
Quantum
Local Chemical Properties ? Scaling Behavior of
Nanostructures Energy Dominance ?
Entropy Dominance of Properties
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Open Source Software ESPResSo
Modular Simulation Package by C. Holm et
al Method development will continue!!
Extensible Simulation Package for Research on
Soft matter
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Central Topics of the Theory Group

• Method Development,
• Scientific Open Source Software (ESPResSo)
• Charged Systems (SFB, Transregio, Gels)
• Long Range Interactions, Hydrodynamics
• Membranes,.Biophysics
• Multiscale Modeling
• Analytic Theory of disordered Systems
• Complex Fluids
• Computational Chemistry of Solvent-Solute Systems
• Melts, Networks Relaxation, NEMD

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COWORKERS L. Delle Site N. Van der Vegt D.
Andrienko, M. Praprotnik, X. Zhou (Los Alamaos
Nat. Lab.) N. Ardikari, W. Schravendijk, M.E.
Lee F. Müller-Plathe ( TU Darmstadt) O. Hahn
(Würzburger Druckmaschinen) D. Mooney (Univ.
College Dublin) H. Schmitz (Bayer AG) W. Tschöp
(DG Bank) S. Leon (UPM Madrid) C. F. Abrams
(Drexel) H. J. Limbach (Nestle)
BMBF Center for Materials Simulation Bayer,
BASF, DSM, Rhodia, Freudenberg
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Why Polycarbonate?
Modern application of Polycarbonate New football
stadium, Cologne, World Championship 2006
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Why study Polycarbonate and the PC/Ni interface?
Grooves and address pits of a die cast sample of
polycarbonate for a high storage density optical
disc
Bayer Materials
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Why study Polycarbonate and the PC/Ni interface?
d?/4 (?100nm)
only high tech commodity polymer
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Specific Adsorption
Two extreme cases end adsorption
only inert surface energy dominated entropy
dominated
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• Structure Property Relations for Polymers -
  Linking Scales
• Interplay universal - system specific aspects

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Soft Matter??

• Thermal energy of particles/ per degree of
  freedom EkT
• Room temperature 300K

Chemical Bond Hydrogen Bond
Soft Matter Thermal Energy dominates properties
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Energy Scale kT for T300K
Electronic structure, CPMD
Quantum Chemistry
Biophysics Membranes, AFM
Spectroscopy
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Time and length scales
?
?
Properties
?
?
generic/universal chemistry specific
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Mixtures Polymer A, B
AA, BB, AB contacts O(N)
Phase separation, critical interaction
chemistry
generic
Intra-chain entropy invariant gt small energy
differences gt phase separation
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Example Viscosity h of a polymer melt
(extrusion processes ....)
Microscopic materials/ chemistry specific
Prefactor L ? 1Å 3Å (e.g.
function of glass transition) T ? 10-13
sec h A MX Energy dominated

Mesoscopic generic/universal Properties L ?
10Å 50Å h A MX X 3.4 T ? 10-8 10-4
sec M molecular weight Entropy dominated
h A MX varies for many decades
varies for many decades

• e.g. M 2M h(2M) ? 10h(M)
• T 500 K 470K
• (T 470 K ) ? 10 h(T 500 K)
• (typical values for BPA-PC)

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Micro-Meso-Macro Simulation
Interplay Energy ? Entropy Free Energy Scale
kBT
(SEMI-)MACROSCOPIC Coarse Graining
Inverse Mapping
MESOSCOPIC Simpler Models Coarse
Graining Inverse Mapping
TODAY
ATOMISTIC/MOLECULAR
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Polycarbonate on Metal Surface

• Linking Scales for Bisphenol-A-Polycarbonate
  (BPA-PC)
• Molecular Coarse-Graining
• Inverse Mapping, (Phenol Diffusion)
• BPA-PC Melts near Nickel Surfaces
• Ab initio calculations Surface/molecule
  energetics
• Multiscale simulation Molecular orientation at
  liquid/metal interface
• Adsorption at a step
• Shearing a melt

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Molecular Coarse-Graining of Bisphenol-A-Polycarbo
nate

• Coarse-grainingmap bead-spring chain over
  molecular structure.
• gt Many fewer degrees of freedom
• Inverse mapping grow atomic structure on top of
  coarse-grained backbone
• gtLarge length-scale equilibrationin an
  atomically resolved polymer

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Mapping Scheme
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Original Ansatz 12 Mapping
Thermodynamic Potential V
Algorithmic speed up !
Distributions include temperature! MD simulation
at one temperature, but with variable
distributions.
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Interaction Energies in the Coarse-Grained Model
Angle potentials are T-dependent Boltzmann
inversions e.g., at carbonate
U
P

• Excluded volume
• Bonds
• Angles
• Torsions

T 570 K
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Molecular Coarse-Graining of Bisphenol-A-Polycarbo
nate Melts
9.3-11.5 Å
A particular conformation of a 10-repeat-unit
molecule of BPA-PC at atomic resolution 356 atoms
Its coarsened representation in the 41 mapping
scheme 43 beads Rg21/2 20.5 Å lp 2 r.u.
Fast motion (e.g. bond vibration) is properly
averaged over CG chain represents a multitude of
underlying atomic structures
C. F. Abrams, KK, Macromol. 36, 260(2003)
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Results for Melts, N20.120

• Molecular Coarse-Grained Melt
• Inverse Mapping

End to end distance of coarse grained
simulations agree to n-scattering experiments!
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Viscosity gt Time Mapping

• Melt simulation
• Viscosity fromchain diffusioncoefficient
• Property of entire chains
• (new data 2005)
• W. Tschöp, K. Kremer, J. Batoulis, T. Bürger, O.
  Hahn, Acta Polym. 49, 61 (1998) ibid. 49, 75.

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How good are generated conformation?Inverse
Mapping Reintroduce Chemical Details
Coarse grained BPA-PC chain
All atom model
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Comparison Simulation n-Scattering
Structure factors of (deuterated) BPA-PC Right
standard BPA-PC Bottom fully deuterated BPA-PC
J. Eilhard, A. Zirkel, W. Tschöp, O. Hahn, K.
K., O. Schärpf, D. Richter,U. Buchenau,J. Chem.
Phys. 110, 1819 (1999)
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Polycarbonate on Metal Surface

• Linking Scales for Bisphenol-A-Polycarbonate
  (BPA-PC)
• Molecular Coarse-Graining
• Phenol Diffusion (need atomistic resolution!)
• Inverse Mapping, (atomistic trajectories for
  entangled melts for up to 10-4sec!!)
• BPA-PC Melts near Nickel Surfaces
• Ab initio calculations Surface/molecule
  energetics
• Multiscale simulation Molecular orientation at
  liquid/metal interface
• Adsorption on a step
• Shearing a melt

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Simulating BPA-PC/Metal Interfaces
Molecular structure coarse-grained onto
bead-spring chain
Simulation of coarse-grainedBPA-PC liquids (T
570K)next to metal surface
Specific surface interactionsinvestigated via ab
initio calculations
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Ab initio Investigations of Comonomeric Analogues
on Nickel
(CPMD Program M. Parrinello)
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CPMD Propane and Carbonic Acid on Nickel

• Adsorption energy ? 0.01 eV (0.2 kT _at_ 570K)
  for d ? 3.2 Å
• Strongly repulsed, regardless of orientation

propane
carbonic acid
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CPMD Benzene and Phenol on Nickel

• Benzene Eads -1.05 eV (21 kT _at_ 570K) at d 2
  Å.
• Phenol Eads -0.92 eV at d 2 Å.
• Both Horizontal orientation strongly preferred,
  short-ranged Eads lt 0.03 eV for d gt 3 Å

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CPMD Dependence of Phenol-Ni Interaction on Ring
Orientation
Interaction verysensitive to orientation!
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CPMD Conclusions

• Strong repulsion of propane and carbonic acid
• the strong orientational dependence
• short interaction range of phenol
• with Ni 111
• ?
• Internal phenylene comonomers in BPA-PC are
  sterically hindered from adsorbing on Ni 111.
  ?
• Torsional freedom in carbonate group allows
  for terminal phenoxy groups to adsorb

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Coarse-Grained BPA-PC with End-Group Resolution
(Dual Scale MD)

• Phenol-Ni interactionstrongly dependent onC1-C4
  phenol orientation
• In standard 41 model,phenoxy end
  orientationnot strictly accounted for
• Resolving only the terminal carbonatesspecifies
  1-4 orientationand is inexpensive

Abrams CF, Delle Site L, KK, PRE 67, 021807
(2003)
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Results Chain-end adsorption
Chain center-of-mass density profiles

• N 10 monomers
• M 240 chains
• ?Rg2?1/2 20.5 Å3 clear regimes
• z lt ?Rg?bulk
• both ends adsorbed
• ?Rg?bulk lt z lt 2?Rg?bulk
• single ends adsorbed
• z gt 2?Rg?bulk
• no ends adsorbed

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Schematic structure of End-Sticky Melts
Chains compressed
Chains elongated
Normal Bulk conformations
? Coupling Surface ?? Bulk?
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Extension I Other Chain EndsEnergy - Entropy
Competition
Delle Site, Leon, KK, JACS, 126, 2944(2004)
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Extension II Stepped Surface
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Line Defect Induced Ordering
L. DelleSite, S. Leon, KK, J. Phys. Cond.
Matt.17, L53, 2005
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Extension III Shearing a Melt
end adsorption energy dominated case phenolic
chain ends Surface Potential for Ends
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Sheared melts
Both ends at surface One end at surface No end at
surface
EPL 70, 264-270 APR 2005
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Extension IV Jamming Lubricants
BPA-PC plus 5 additives
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Extension IV Jamming Lubricants
BPA-PC plus 5 additives
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Jamming Lubricants
BPA-PC plus 5 (weight) additives under
shear BPA-PC 5-mers
BPA-PC DPC
Blue major component
Yellow minor component
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Jamming Lubricants
BPA-PC plus 5 additives under shear
JCP 123 Art. No. 104904 SEP 8 2005
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Specific Surface Morphologies Multiscale
Approach
PC near Ni Competition Energy- Entropy
Coarse-graining onto bead-spring chain
Simulation of coarse-grainedpolymer next to
metal surface (BPA-PC)
sticky chain ends neutral
Coating/contamination with oligomers
Specific surface interactions ab initio
calculations (CPMD)
C.F. Abrams, et al. PRE 021807 (2003) L.
DelleSite, et al. PRL 156103 (2002) BMBF Zentrum
MatSim
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A few Challenges

• Dual-Triple Scale Simulations/Theory
• Adaptive quantum?force field?coarse grained
• Nonbonded Interactions NEMD, Morphology
• Accuracy kBTO(1/N) needed!
• Conformations ? Electronic Properties
• E.g. coupling of aromatic groups to
• backbone conformation,
• or to other chains
• Online Experiments
• Nanoscale Experiments, long Times

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Adaptive MethodsChanging degrees of freedom on
the fly
Adaptive Multiscale methods Static and Dynamic
Simple test case Polymers at surfaces, VW
Foundation Project M. Praprotnik, L. DelleSite,
KK, JCP, Nov. 2005
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Adaptive MethodsChanging degrees of freedom on
the fly
Tetrahedron, repulsive LJ Particles, ?
Hybrids ? Softer Sphere FENE
bonds Explicit Atom ?
Transition ? Coarse Grained regime
regime regime
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Requirements

• Same center-center g(r)
• Same mass density
• Same Pressure (gtEq. of state)
• Same temperature
• Free exchange between regimes
• Simple two body potential

• Can be viewed as 1st order phase
• transition
• Phase equilibrium
• Thermostat has to provide/take out
• latent heat due to change in degrees
• of freedom

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Coarse Grained Model
Study explicite atom and CG system seperately gt
fit CG Interaction Potential
?ex ?cg, pexpcg, TexTcg
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Transition Regime
explicit hybrid coarse grained
Interactions explicit-explicit CG-CG hybrid-hybri
d CG- hybrid CG-CG explicit-hybrid
explicit-explicit
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Particle Numbers, Density
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Particle Exchange
Radial Distributions, Number of neighbours
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Adaptive MethodsChanging degrees of freedom on
the fly

• Practical proof of principle
• Many open questions
• Higher densities
• real systems
• Inhomogeneous systems
• Dynamics
• Other geometries
• Multi level systems

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A few Challenges

• Dual-Triple Scale Simulations/Theory
• Adaptive quantum?force field?coarse grained
• Nonbonded Interactions NEMD, Morphology
• Accuracy kBTO(1/N) needed!
• Conformations ? Electronic Properties
• E.g. coupling of aromatic groups to
• backbone conformation,
• or to other chains
• Online Experiments
• Nanoscale Experiments, long Times

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Solute Solvent Systems van der Vegt, DelleSite
Combined CPMD and atomistic simulations for
benzene adsorption out of water gt Extension to
more complicated systems
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Ad-/Desorption Process
P. Schravendijk, N. van der Vegt, L. Delle Site,
KK, ChemPhysChem 6, 1866 (2005)
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A few Challenges

• Dual-Triple Scale Simulations/Theory
• Adaptive quantum?force field?coarse grained
• Nonbonded Interactions NEMD, Morphology
• Accuracy kBTO(1/N) needed!
• Conformations ? Electronic Properties
• E.g. coupling of aromatic groups to
• backbone conformation,
• or to other chains
• Online Experiments
• Nanoscale Experiments, long Times