Nano tools for macro problems: multiscale molecular ... - SFGP

University of Trieste
Nano tools for macro
problems: multiscale
molecular modeling for life
and materials science
Maurizio Fermeglia
MOSE –DI3 ‐ University of Trieste
Via valerio 10, 34127 Trieste (Italy)
Maurizio.Fermeglia@di3.units.it
mose.units.it
Department of Industrial Engineering &
Information Technology

The technology vision 2020
InMother 2012
Lyon, 20 April 2012 - 2

Horizon2020 Structure
KET
InMother 2012
Lyon, 20 April 2012 - 3

Introduction of new generation of products and
productive processes (2000‐2020)
• Timeline for beginning of industrial prototyping and nanotechnology
commercialization
InMother 2012
Lyon, 20 April 2012 - 4

Multiscale Molecular Modeling
CHARACTERISTIC TIMES
years
Engineering
design
hours
minutes
seconds
microseconds
nanoseconds
Atomistic
simulation
(atoms)
Mesoscale
modeling
(groups of
atoms or
molecules)
Process
simulation
FEM
(continuum)
picoseconds
femtoseconds
Quantum
mechanics
(electrons)
1Å
1nm 1μm 1mm 1m
CHARACTERISTIC LENGHTS
InMother 2012
Lyon, 20 April 2012 - 5

Many scale Molecular Modeling
CHARACTERISTIC TIMES
years
Engineering
design
hours
minutes
seconds
microseconds
nanoseconds
Atomistic
simulation
(atoms)
Mesoscale
modeling
(groups of
atoms or
molecules)
Process
simulation
FEM
(continuum)
picoseconds
femtoseconds
Quantum
mechanics
(electrons)
1Å
1nm 1μm 1mm 1m
CHARACTERISTIC LENGHTS
InMother 2012
Lyon, 20 April 2012 - 6

Modelling and experiments
InMother 2012
Lyon, 20 April 2012 - 7

• Introduction
Outline of talk
– Multiscale Molecular Modeling
• Mapping procedure
– From atomistic simulation to mesoscale
– From mesoscale to micro FEM
• Applications to materials science
– Polymer clay nanocomposites
– Self assembly of nanoparticles in block copolymers
• Applications to life science
– Block copolymers for drug delivery
• Conclusions
InMother 2012
Lyon, 20 April 2012 - 8

From atoms … to beads
Molecular Dynamics
Dissipative Particle Dynamics
ForceField based calculations
Soft potentials calculations
F i = f (a ii , a ij , …, r c )
• Polymeric materials are modeled
by connecting beads by
harmonic springs
InMother 2012
Lyon, 20 April 2012 - 9

From atoms … to beads
• The parameters for Mesoscale (MesoDyn or DPD) are
– the bead size and Gaussian chain architecture
– the bead mobilities M,
– the effective Flory‐Huggins interactions
• Method 1: polymer blends, copolymers, spherical nanofillers
– bead size and Gaussian chain architecture: by MD
• from characteristic ratio (C) in terms of Kuhn length
– mobility: by Molecular Dynamics
• Bead self diffusion coefficients
– FH interactions: by Molecular Dynamics
• Differences in non bonded energies between bulk and isolated chain
• Method 2: nanofillers of any size and shape
– bead size and Gaussian chain architecture: by MD
• from characteristic ratio (C) in terms of Kuhn length
– mobility: by Molecular Dynamics
• Bead self diffusion coefficients
– Interaction parameters are determined directly from energy distribution in
MD
• Considering density distribution around nanofiller
InMother 2012
Lyon, 20 April 2012 - 10

Method 1: bead size, chain architecture
• MD NPT runs on homo polymers
– Monomer length
– C ∞ calculation and Kuhn lenght
– Chain architecture
r
r
2
max
0
C
NL
nl
2
NL
2
Rotational Isomeric State
C1 C2 C3 C4 Cn
MM minimization and annealing
MD - NPT
2 – end to end distance
2 / n l 2 = C∞
Change
chain
lenght
Cinf(% )
100
90
80
70
60
50
40
30
20
10
0
0 50 100 150 200
N
Fermeglia, M. et al., Polymer, 47:5979‐5989 (2006)
InMother 2012
C∞
Lyon, 20 April 2012 - 11

Method 1: F‐H interaction parameter chi
• Molecular dynamics NPT and NVT runs
E
coh
E
periodic
nb
E
isolated
nb
E
RT
mix
V
mon
E
mix
1
E
V
coh
pure1
2
E
V
coh
pure2
E
V
coh
mix
a
AB
a
3.271
3.9
AA 0. 51
nDPD
AB
Fermeglia, M. and Pricl S., AIChE J., 2619 (45), 1999
InMother 2012
Lyon, 20 April 2012 - 12

Method 2: Mapping DPD parameters
Single, binary, ternary
energies from MD
Binding energies are
rescaled considering the
number of contacts
tot
E n E n E 2
sys
ii ii
jj jj
n
ij
E
ij
Binding energies from MD
(vdW + Coulomb)
References DPD
Interactions are selected
Equal beads aij 25
Define DPD beads
(head, tail, …) and
recalculate energies
DPD matrix parameters
(scaling from references)
Strong repulsive beads
aij >25
Density profiles from MD =? Density profiles from DPD
Scocchi et al., J. Phys. Chem. B,
(2007), 111, 2143
InMother 2012
Lyon, 20 April 2012 - 13

From beads to micro FEM
Dissipative Particle Dynamics
Micro ‐ FEM Simulation
FEM Analysis:
Macroscopic
properties
Soft potentials calculations
F i = f (a ii , a ij , …, r c )
Characteristic dimension of mesoscopic
system
Toth R., Santese F., Pereira S.P., Romero‐Nieto D., Pricl S., Fermeglia M., Posocco, Journal of Materials Chemistry, 2012
InMother 2012
Lyon, 20 April 2012 - 14

From beads … to micro: fixed grid
• Geometry: map cubes to Palmyra
tetrahedrons
• Laplace equation is solved for
electric conductance,
diffusion and permeability
• Local deformation allow the
calculation of mechanical
properties
Atomistic
Mesoscale
Fixed grid
Variable grid
Physical Prop.
InMother 2012
Lyon, 20 April 2012 - 15