4 research outputs found
Deformation of polymer films by bending forces
We study the deformation of nano--scale polymer films which are subject to
external bending forces by means of computer simulation. The polymer is
represented by a generalized bead--spring--model, intended to reproduce
characteristic features of n--alkanes. The film is loaded by the action of a
prismatic blade which is pressed into the polymer bulk from above and a pair of
columns which support the film from below. The interaction between blade and
support columns and the polymer is modelled by the repulsive part of a
Lennard-Jones potential. For different system sizes as well as for different
chainlengths, this nano--scale experiment is simulated by molecular dynamics
methods. Our results allow us to give a first characterization of deformed
states for such films. We resolve the kinetic and the dynamic stage of the
deformation process in time and access the length scale between discrete
particle and continuum mechanics behaviour. For the chainlengths considered
here, we find that the deformation process is dominated by shear. We observe
strangling effects for the film and deformation fluctuations in the steady
state.Comment: 15 pages, 8 figure
Modelling of amorphous polymer surfaces in computer simulation
We study surface effects in amorphous polymer systems by means of computer
simulation. In the framework of molecular dynamics, we present two different
methods to prepare such surfaces. {\em Free} surfaces are stabilized solely by
van--der--Waals interactions whereas {\em confined} surfaces emerge in the
presence of repelling plates. The two models are compared in various computer
simulations. For free surfaces, we analyze the migration of end--monomers to
the surface. The buildup of density and pressure profiles from zero to their
bulk values depends on the surface preparation method. In the case of confined
surfaces, we find density and pressure oszillations next to the repelling
plates. We investigate the influence of surfaces on the coordination number, on
the orientation of single bonds, and on polymer end--to--end vectors.
Furthermore, different statistical methods to determine location and width of
the surface region for systems of various chain lengths are discussed and
applied. We introduce a ``height function'' and show that this method allows to
determine average surface profiles only by scanning the outermost layer of
monomers.Comment: 23 pages, 12 figure
Modelling of Amorphous Polymer Surfaces in Computer Simulation
We study surface effects in amorphous polymer systems by means of computer simulation. In the framework of molecular dynamics, we present two different methods to prepare such surfaces. Free surfaces are stabilized solely by van--der--Waals interactions whereas confined surfaces emerge in the presence of repelling plates. The two models are compared in various computer simulations. For free surfaces, we analyze the migration of end--monomers to the surface. The buildup of density and pressure profiles from zero to their bulk values depends on the surface preparation method. In the case of confined surfaces, we find density and pressure oszillations next to the repelling plates. We investigate the influence of surfaces on the coordination number, on the orientation of single bonds, and on polymer end--to--end vectors. Furthermore, different statistical methods to determine location and width of the surface region for systems of various chain lengths are discussed and applied. We introdu..