Incollection,
Molecular dynamics study of the flow properties of a polymeric liquid confined by a soft substrate
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)
Abstract
We studied the flow properties of a polymer melt confined between polymer
brush layers, by means of molecular dynamics simulations. The brush serves as
a model of a soft, deformable and elastic substrate whose properties are tuned
in the simulation changing the grafting density. Brush and polymer melt are
composed of bead-spring chains of identical chemical identity and modeled with
well-established coarse-grained potentials that retain the main properties of
the chains. The temperature is held constant with a Dissipative Particle
Dynamics thermostat that keeps the hydrodynamic correlations in the system.
Moving the confining walls at constant velocity or applying an external volume
force, Couette and Poiseuille flows are imposed to the system and the
velocity and density profiles are obtained from the simulations, as a function
of shear rate or external force. Boundary conditions (slip length and
velocity) of this non-newtonian liquid are measured directly from the
simulations, as function of the grafting density of the brush layer. The
characteristics of the brush-melt interface, morphology and dynamics of the
chains are also obtained. We observe an interesting inversion of the flow
velocity in the vicinity of the brush-melt interface, due to non-trivial
cyclic dynamics of the grafted chains.
