Transcript Presentation (PowerPoint File)

Multiscale Simulation of
Polymers
near (Metal) Surfaces
K. Kremer
Max Planck Institute for Polymer Research, Mainz
09/2005
Max-Planck Institute for Polymer Research
Mainz
Characteristic Time and Length Scales
Soft fluid
Finite
elements
Time
Atomistic
Quantum
bilayer
Molecular
buckles
Length
Local Chemical Properties  Scaling Behavior of Nanostructures
Energy Dominance  Entropy Dominance of Properties
Open Source Software:
ESPResSo
Modular Simulation Package by C. Holm et al
Method development will continue!!
Extensible Simulation Package
for Research on Soft matter
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 …
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
Why Polycarbonate?
Modern application of Polycarbonate
New football stadium, Cologne, World Championship 2006
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
Why study Polycarbonate and the
PC/Ni interface?
d=λ/4
(100nm)
“only” high tech commodity polymer
Specific Adsorption
Two extreme cases
end adsorption only
“inert” surface
energy 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:
E  1.38 1023 J / K  300K
 21
 4.1 10
Chemical Bond
Hydrogen Bond
J  kT
19
E  3 10 J  80kT
E  6kT  10kT
Soft Matter: Thermal Energy dominates properties
Energy Scale kT for T=300K
23
E  1.38 10
 21
kT  4.1 10
J / K  300K
J
2
kT  2.5 10 eV
Electronic structure, CPMD
kT  9.5 104 EH
Quantum Chemistry
kT  4.1 pNnm
Biophysics Membranes, AFM
1
Spectroscopy
kT  200cm
kT  0.6kcal / m ol
kT  2.5kJ / m ol
Time and length scales


Semi macroscopic
L  100Å - 1000Å
T  0 (1 sec)
Macroscopic
domains etc.
Mesoscopic
L  10Å - 50Å
T  10-8 - 10-4 sec
Entropy dominates
Properties

Mesoscopic
L  10Å - 50Å
T 10-8 - 10-4 sec
Entropy dominates
generic/universal

Microscopic
L  1Å - 3Å
T  10-13 sec
Energy dominates
***
(Sub)atomic
electronic structure
chemical reactions
excited states
chemistry specific
Mixtures Polymer A, B
#AA, #BB, #AB contacts =O(N)
R (N )  N
2
U AB  N AB
U AA  U BB  N
 eff   AB  
Phase separation, critical interaction
c
1
eff
  const N
“chemistry”
“generic”
Intra-chain entropy invariant => small energy differences => phase separation
Example Viscosity h of a polymer melt
(extrusion processes ....)
Microscopic
materials/ chemistry specific Prefactor
L  1Å – 3Å
(e.g. function of TG , glass transition)
h  A MX
T  10-13 sec
“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
h(T =470 K )  10 h(T  500 K)
(typical values for BPA-PC)
Micro-Meso-Macro
Interplay Energy  Entropy
Simulation
Free Energy Scale:
kBT
(SEMI-)MACROSCOPIC
“Coarse Graining“
Inverse Mapping
MESOSCOPIC
Simpler Models
/
“Coarse Graining“
Inverse Mapping
ATOMISTIC MOLECULAR
TODAY
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
Molecular Coarse-Graining of
Bisphenol-A-Polycarbonate
Coarse-graining:
map bead-spring chain over
molecular structure.
=> Many fewer degrees of freedom
Inverse mapping: grow atomic
structure on top of coarsegrained backbone
=>Large length-scale equilibration
in an atomically resolved polymer
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
O
C
O
1:2 Mapping
C
C
O
O
O
v
v
P( l , a , j )  P( l )P( a )P( j )
v v
v
P( l , b , j )  P( l )P( b )P( j )
}
Thermodynamic Potential
V (l , b ,j )
C
O
V
Distribution
Functions
Algorithmic speed
up:  104 !
  ln P(l , b ,j )
 ln P(l )  ln P( b )  ln P(j )}
Distributions include temperature!
MD simulation at one temperature, but with variable distributions.
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
Molecular Coarse-Graining of
Bisphenol-A-Polycarbonate 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
4:1 mapping scheme; 43 “beads”;
‹Rg2›1/2 = 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)
Results for Melts, N=20….120
– Molecular Coarse-Grained Melt
– Inverse Mapping
End to end distance of coarse grained simulations
agree to n-scattering experiments!
2
G
o 2
R (N )
N
 37 A
Viscosity => Time Mapping
h  R k T s ( N 1) 36D
2
N B
3
2
• Melt simulation
• Viscosity from
chain diffusion
coefficient
• Property of entire
chains
  2.2 1011 sec
(new data 2005)
[W. Tschöp, K. Kremer, J. Batoulis, T. Bürger, O. Hahn, Acta Polym. 49, 61
(1998); ibid. 49, 75].
How good are generated conformation?
Inverse Mapping:
Reintroduce Chemical Details




All atom model
Coarse grained
BPA-PC chain
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)]
Polycarbonate on Metal Surface
• Linking Scales for Bisphenol-A-Polycarbonate (BPAPC)
– 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
Molecular structure coarse-grained
onto bead-spring chain
Simulation of coarse-grained
BPA-PC liquids (T = 570K)
next to metal surface
Specific surface interactions
investigated via ab initio
calculations
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 very
sensitive 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 EndGroup Resolution (Dual Scale MD)
•Phenol-Ni interaction
strongly dependent on
C1-C4 phenol orientation
•In standard 4:1 model,
phenoxy end orientation
not strictly accounted for
•Resolving only the
terminal carbonates
specifies 1-4 orientation
and is inexpensive
Abrams CF, Delle Site L, KK, PRE 67, 021807 (2003)
Results: Chain-end adsorption
Chain center-of-mass
density profiles
N = 10 monomers
M = 240 chains
Rg21/2 = 20.5 Å
3 clear regimes:
• z < Rgbulk :
both ends adsorbed
• Rgbulk < z <
2Rgbulk :
single ends adsorbed
• z > 2Rgbulk:
no ends adsorbed
Schematic structure of
“End-Sticky” Melts
Chains “compressed”
Chains “elongated”
Normal Bulk conformations
 Coupling Surface  Bulk?
Extension I: Other Chain Ends
Energy - 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

 0




  Rouse
1
 10 Rouse
1
Sheared melts


Both ends at surface
One end at surface
No end at surface
 100 Rouse
1
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
Blue: major component
BPA-PC + DPC
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
Coarse-graining
onto beadspring chain
PC near Ni
Competition Energy- Entropy
Simulation of
coarse-grained
polymer next to
metal
surface (BPAPC)
Specific surface
interactions
ab initio
calculations
(CPMD)
“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
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
Adaptive Methods:
Changing 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
Adaptive Methods:
Changing degrees of freedom on the fly
Tetrahedron,
repulsive LJ Particles, 
FENE bonds
Explicit Atom
regime
Hybrids
 Transition
regime

“Softer” Sphere
 Coarse Grained
regime
Requirements
Same center-center g(r)
Same mass density
Same Pressure (=>Eq. 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
Coarse Grained Model
Study explicite atom and CG system
seperately
=> fit CG Interaction Potential:
U (r )   {1  exp[ (r  r0 )]}
cm
ex = cg, pex=pcg, Tex=Tcg
2
Transition Regime
explicit
hybrid coarse grained
Fab 
w( X a ) w( X b ) Fab 
atom
[1  w( X a )W ( X b )]Fab
cm
Interactions
explicit-explicit
CG-CG
hybrid-hybrid
CG- hybrid:
CG-CG
explicit-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” systems
Inhomogeneous systems
Dynamics
Other geometries
Multi level systems
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
Solute Solvent Systems
van der Vegt, DelleSite
Combined CPMD and atomistic simulations
for 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 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