Simulation of Structure, Properties and Behavior
Dhiraj K. Mahajan,a Anatoly V. Berezkin,b P. Ulrich Biedermann, b Fathollah Varnik,a
Alexander Hartmaier a
a ICAMS, Ruhr-Universität Bochum, b Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf
Role of Substrate Roughness
Linear/cross-linked polyurethane film on the ZnO surface
• ZnO(0001)-Zn-O/OH single crystal surface: well
characterized by experiment, stable at ambient conditions.
• Polyurethane. The behavior of some typical molecules and
polymer fragments are considered to extend existing
OPLS-AA force filed to the polyurethane case.
water methyl acetate methyl isocyanate N-methyl-acetamide
, , , …
LEED images obtained at 63 eV
Polyurethane Network: Curing, Structure and Properties
nPPO = 2, 5, 8
branched polypropylene ether triol
(Desmophen 1380 BT)
4,4'-methylene diphenyl diisocyanate
All-atom network model
Conversion vs. time
Glass transition temperature Stress-strain curves Young modulus
• Metals are usually coated with polymers against corrosion.
The objective of this project is to develop an atomistic
understanding of the interphase/interface structure of
polymer/metal oxide contacts and the diffusion mechanism
of ions and small molecules (H2O, O2) along the interface
as a guide for future material design.
• Multiscale computer simulation
• Kinetics of curing during polymer coating formation;
• Interfacial structure of coating;
• Permeability of coating and mechanisms of substrate
- structure, charge, and
conformation of small molecules;
- molecule-surface interactions
Atomistic simulation (MD)
- adsorption phenomena;
- diffusivity, viscoity, density,
cohesion energy of components;
Calibration of atomistic force-field (OPLS)
Coarse-grained level (MD)
- kinetics of curing;
- coating strucutre;
- corrosion mechanisms;
Parameterization of coarse-grained model
Adsorption of Small Organic Molecules (Density Functional Theory + Classical Simulations)
Water, methyl acetate, methyl isocyanate.
Adsorbed configurations and
energies of adsroprtion
Iterative improvement of FF
Adsorption energy of H20
Adsorption energy of
Comparison of classical and DFT
Polyurethane Structure at ZnO Interface
• Polymer/substrate coating systems are generally characterized
by rough substrate surfaces with undulations ranging from few
nanometers to several micrometers. It is known that the surface
roughness strengthens the polymer/substrate bonding either by
increasing the effective contact area or by mechanical
interlocking of polymer between surface undulations. However,
little is known regarding the role of relative dimensions of
polymer chains with respect to surface undulations in effecting
the polymer bonding. Such information can be used in substrate
surface engineering for improving bonding without changing the
interface chemistry, which forms the objective of this part of the
Molecular Dynamics Simulation Details
Effect of Substrate Roughness
• An ideal coating system is obtained
by equilibrating the coarse-grained
polymer molecules between thin
atomic layer at the top and planar
atomic substrate at the bottom.
• After polymer equilibration, coating
systems with varying substrate
roughness is obtained by removing
atoms from the planar substrate in
regular pattern with dimensions of
the order of Rg.
• Polymer molecules interacts with the
atomic substrate and top layer using
non-bonded Lennard-Jones potential.
• Zero pressure initial configuration of
different coating systems is obtained
by allowing motion of top layer atoms
Various rough substrates studied
Statistical dimensions of polymer molecule
Failed configuration of various coating systems at similar strain under Mode I loading
Mode I loading applied
to coating system
Deformation behavior of various coating systems under Mode I
loading with different substrate roughness.
Work of separation versus roughness factor for different substrate
roughness samples shows a vital role of mechanical interlocking in
strengthening the interface in contrast to the contribution of
increased effective area of contact as shown by a linear fit.
• Coarse-grained Molecular Dynamics simulations
Rough surfaces strengthen the interface by
increasing the effective contact area
Mechanical interlocking is another mechanism
responsible for strengthening the interface
R. Van Tijum, PhD thesis, University of Groningen, 2006
Polymer/substrate interactions play an important role in coatings and composite materials, applications of which
includes renewable energy production structures, sandwich panels used in automobiles and packaging. Desired
properties of these materials include high adhesion strength of polymer with substrate and corrosion resistance
of the substrate, among others. Polymer/substrate interfaces are essentially characterized by the network
structure of the polymer and substrate roughness that plays a vital role in imparting the desired properties to
these materials. The objective of the present project is to understand the mechanism(s) responsible for
adhesion of polymer on substrates and to quantify the role of substrate roughness as well as polymer network
structure on the desired properties of the coating system. At this stage of the project, the individual roles of
substrate roughness and network structure are studied separately using multi-scale simulation methodology.
The outcome of these complementary studies will improve our understanding of polymer/substrate interface
structure, properties and behavior and may be used as guide for future material design.
Polymer/Solid interfaces finds several technological applications such as renewable energy
production structures, sandwich panel for automobiles and packaging.
Measure of roughness
• F. Varnik and K. Binder, Multiscale modeling of polymers at interfaces, Int. J. Mat Res, 100, 1494-1502,
• J. Rottler and M.O. Robbins, Molecular simulations of deformation and failure in bonds formed by glassy
polymer adhesives. J. Adh. Sc. Tech. 17, 369-381, (2003).
• A. V. Berezkin, P. U. Biedermann and A. A. Auer, Mesoscale simulation of network formation and
structure, combining molecular dynamics and kinetic Monte Carlo approaches, In proceeding: European
Polymer Congress 2011, 1378.
Slide Number 1