multiscale simulation of polymers near (metal) surfaces k. kremer max planck institute for polymer...
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Multiscale Simulation of Polymers
near (Metal) SurfacesK. Kremer
Max Planck Institute for Polymer Research, Mainz
09/2005
Max-Planck Institute for Polymer Research Mainz
Time
Quantum
Atomistic
Soft fluid
Local Chemical Properties Scaling Behavior of Nanostructures Energy Dominance Entropy Dominance of Properties
Finiteelements
Characteristic Time and Length Scales
Length
bilayerbucklesMolecular
Open Source Software: ESPResSo
Extensible Simulation Package for Research on Soft matter
Modular Simulation Package by C. Holm et alMethod development will continue!!
Central Topics of the Theory Group
Method Development, Scientific Open Source Software (ESPResSo)Charged Systems (SFB, Transregio, Gels)Long Range Interactions, HydrodynamicsMembranes,….Biophysics
Multiscale ModelingAnalytic Theory of disordered SystemsComplex FluidsComputational Chemistry of Solvent-Solute SystemsMelts, Networks – Relaxation, NEMD …
COWORKERS:L. Delle SiteN. 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 SimulationBayer, BASF, DSM, Rhodia, Freudenberg
Modern application of PolycarbonateNew football stadium, Cologne, World Championship 2006
Why Polycarbonate?
Grooves and address pits of a die cast sample of polycarbonate for a high storage density optical disc
Bayer Materials
Why study Polycarbonate and the PC/Ni interface?
Why study Polycarbonate and the PC/Ni interface?
“only” high tech commodity polymer
d=λ/4(100nm)
Specific Adsorption
Two extreme casesend adsorption only “inert” surfaceenergy dominated entropy dominated
• Structure Property Relations for Polymers - Linking Scales – Interplay universal - system specific
aspects
Soft Matter??Thermal energy of particles/ per degree of freedom
E=kT Room temperature 300K:
kTJ
KKJE
21
23
101.4
300/1038.1
Chemical Bond
Hydrogen Bond kTkTE
kTJE
106
80103 19
Soft Matter: Thermal Energy dominates properties
molkJkT
molkcalkT
cmkT
pNnmkT
EkT
eVkT
JkT
KKJE
H
/5.2
/6.0
200
1.4
105.9
105.2
101.4
300/1038.1
1
4
2
21
23
Energy Scale kT for T=300K
Quantum Chemistry
Electronic structure, CPMD
Biophysics Membranes, AFM
Spectroscopy
Time and length scales
(Sub)atomicelectronic structurechemical reactionsexcited states
MicroscopicL 1Å - 3ÅT 10-13 secEnergy dominates
MesoscopicL 10Å - 50ÅT 10-8 - 10-4 secEntropy dominates
MesoscopicL 10Å - 50ÅT 10-8 - 10-4 secEntropy dominates
Semi macroscopicL 100Å - 1000ÅT 0 (1 sec)
Macroscopicdomains etc.
generic/universal *** chemistry specific
Properties
Mixtures Polymer A, B#AA, #BB, #AB contacts =O(N)
1 Nconstceff
Phase separation, critical interaction
Intra-chain entropy invariant => small energy differences => phase separation
“chemistry” “generic”
ABeff
BBAA
ABAB
NUU
NUNNR )(2
Microscopic materials/ chemistry specific Prefactor
L 1Å – 3Å (e.g. function of glass transition)
T 10-13 sec A MX
“Energy dominated“
,TG
Example Viscosity of a polymer melt (extrusion processes ....)
A MX
varies for many decades
varies for many decades
e.g.: M 2M T =500 K 470K(T =470 K ) T
(typical values for BPA-PC)
Mesoscopic generic/universal Properties
L 10Å – 50Å A MX X = 3.4
T 10-8 – 10-4 sec M molecular weight“Entropy dominated“
Micro-Meso-Macro
Simulation
(SEMI-)MACROSCOPIC“Coarse Graining“ Inverse Mapping
MESOSCOPICSimpler Models
“Coarse Graining“ Inverse Mapping
ATOMISTIC/MOLECULAR
TODAY
Interplay Energy Entropy
Free Energy Scale: kBT
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
Coarse-graining:map bead-spring chain over molecular structure.=> Many fewer degrees of freedom
Inverse mapping: grow atomic structure on top of coarse-grained backbone=>Large length-scale equilibrationin an atomically resolved polymer
Molecular Coarse-Graining of Bisphenol-A-Polycarbonate
Mapping Scheme
Quantum Chemistry
Monte Carlo, isolated
all atom chain
sample CG distributions on basis of all atom chain
Intra-chain potentials
for CG melts at given temperature
Original Ansatz 1:2 Mapping
O C O
O
C O C O
O
C
))P()P(P(),,P( ll
))P()P(P(),,P( ll
DistributionFunctions
Thermodynamic Potential V
Distributions include temperature! MD simulation at one temperature, but with variable distributions.
Algorithmic speed up : !410
)(ln)(ln)(ln
),,(ln),,(
PPlP
lPlV
Interaction Energies in the Coarse-Grained Model
• Excluded volume• Bonds• Angles• Torsions
U
P
Angle potentials are T-dependent Boltzmann inversions; e.g., at carbonate:
T = 570 K
Fast motion (e.g. bond vibration) is properly averaged over;CG chain represents a multitude of underlying atomic structures
Molecular Coarse-Graining of Bisphenol-A-Polycarbonate Melts
A particular conformation ofa 10-repeat-unit moleculeof BPA-PC at atomic resolution;356 atoms
Its coarsened representation in the4:1 mapping scheme; 43 “beads”;
‹Rg2›1/2 = 20.5 Å; lp ~ 2
r.u.
9.3-11.5 Å
C. F. Abrams, KK, Macromol. 36, 260(2003)
Results for Melts, N=20….120
– Molecular Coarse-Grained Melt– Inverse Mapping
End to end distance of coarse grained simulationsagree to n-scattering experiments!
22
A37)( o
G
NNR
Viscosity => Time Mapping
• Melt simulation• Viscosity from
chain 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].
DNsTkR BN 36)1( 232
sec102.2 11
How good are generated conformation?Inverse Mapping:
Reintroduce Chemical Details
Coarse grained BPA-PC chain
All atom model
Structure factors of (deuterated) BPA-PC
Right: standard BPA-PCBottom: 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)]
Comparison: Simulation n-Scattering
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
Simulating BPA-PC/Metal Interfaces
Simulation of coarse-grainedBPA-PC liquids (T = 570K)next to metal surface
Specific surface interactionsinvestigated via ab initio calculations
Molecular structure coarse-grainedonto bead-spring chain
Ab initio Investigations of Comonomeric Analogues on Nickel
(CPMD Program: M. Parrinello)
CPMD: Propane and Carbonic Acid on Nickel
Adsorption energy: +0.01 eV (0.2 kT @ 570K) for d 3.2 Å Strongly repulsed, regardless of orientation
propane
carbonic acid
CPMD: Benzene and Phenol on Nickel
• Benzene: Eads = -1.05 eV (21 kT @ 570K) at d = 2 Å.
• Phenol: Eads = -0.92 eV at d = 2 Å.
• Both: Horizontal orientation strongly preferred, short-ranged: |Eads| < 0.03 eV for d > 3 Å
CPMD: Dependence of Phenol-Ni Interaction on Ring Orientation
Interaction verysensitive to orientation!
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
Coarse-Grained BPA-PC with End-Group Resolution (Dual Scale MD)
•Phenol-Ni interactionstrongly dependent onC1-C4 phenol orientation
•In standard 4:1 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)
Results: Chain-end adsorption
N = 10 monomersM = 240 chainsRg
21/2 = 20.5 Å
3 clear regimes:• z < Rgbulk :
both ends adsorbed• Rgbulk < z < 2Rgbulk :
single ends adsorbed
• z > 2Rgbulk:no ends adsorbed
Chain center-of-massdensity profiles
Schematic structure of “End-Sticky” Melts
Chains “compressed”
Chains “elongated”
Normal Bulk conformations
Coupling Surface Bulk?
Extension I: Other Chain EndsEnergy - Entropy Competition
Delle Site, Leon, KK, JACS, 126, 2944(2004)
Extension II: Stepped Surface
Line Defect Induced Ordering
L. DelleSite, S. Leon, KK, J. Phys. Cond. Matt.17, L53, 2005
Extension III: Shearing a Melt
end adsorption energy dominated case:phenolic chain ends
Surface Potential for Ends
Sheared melts
0
1
Rouse 1
10
Rouse
1100
Rouse
Both ends at surfaceOne end at surfaceNo end at surface
EPL 70, 264-270 APR 2005
Extension IV: Jamming Lubricants
BPA-PC plus 5% additives
Extension IV: Jamming Lubricants
BPA-PC plus 5% additives
Jamming Lubricants
BPA-PC plus 5% (weight) additives under shear:
BPA-PC + 5-mers BPA-PC + DPC
Blue: major component Yellow: minor component
Jamming Lubricants
BPA-PC plus 5% additives under shear:
JCP 123 Art. No. 104904 SEP 8 2005
Specific Surface Morphologies – Multiscale Approach
PC near Ni Competition Energy- Entropy
“sticky” chain ends “neutral”Coating/contamination with oligomers
C.F. Abrams, et al. PRE 021807 (2003)L. DelleSite, et al. PRL 156103 (2002)BMBF Zentrum MatSim
Coarse-grainingonto bead-spring chain
Simulation of coarse-grainedpolymer next to metal surface (BPA-PC)
Specific surface interactions ab initio calculations (CPMD)
A few Challenges • Dual-Triple… Scale Simulations/Theory
– Adaptive quantumforce fieldcoarse 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
Simple test case
Polymers at surfaces,VW Foundation ProjectM. Praprotnik, L. DelleSite, KK, JCP, Nov. 2005
Adaptive Methods:Changing degrees of freedom on the fly
Adaptive Multiscale methods – Static and Dynamic
Adaptive Methods:Changing degrees of freedom on the fly
Tetrahedron, repulsive LJ Particles, Hybrids “Softer” SphereFENE bonds
Explicit Atom Transition Coarse Grainedregime regime regime
Same center-center g(r)Same mass densitySame Pressure (=>Eq. of state)Same temperatureFree 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
Requirements
ex = cg, pex=pcg, Tex=Tcg
Study explicite atom and CG systemseperately => fit CG Interaction Potential:
20)]}(exp[1{)( rrrU cm
Coarse Grained Model
Transition Regime
cm
atom
FXWXw
FXwXw
F
)]()(1[
)()(
explicit hybrid coarse grained
Interactions
explicit-explicitCG-CGhybrid-hybrid
CG- hybrid: CG-CGexplicit-hybrid: explicit-explicit
Particle Numbers, Density
Particle Exchange Radial Distributions, Number of neighbours
Adaptive Methods:Changing degrees of freedom on the fly
Practical proof of principle
Many open questions:
Higher densities“real” systemsInhomogeneous systemsDynamicsOther geometriesMulti level systems
A few Challenges • Dual-Triple… Scale Simulations/Theory
– Adaptive quantumforce fieldcoarse 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
Solute Solvent Systems van der Vegt, DelleSite
Combined CPMD and atomistic simulationsfor benzene adsorption out of water=> Extension to more complicated systems
Ad-/Desorption Process
P. Schravendijk, N. van der Vegt, L. Delle Site, KK, ChemPhysChem 6, 1866 (2005)
A few Challenges • Dual-Triple… Scale Simulations/Theory
– Adaptive quantumforce fieldcoarse 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