Search results for "dynamics"
showing 10 items of 9782 documents
Anomalous Structure and Scaling of Ring Polymer Brushes
2011
A comparative simulation study of polymer brushes formed by grafting at a planar surface either flexible linear polymers (chain length $N_L$) or (non-catenated) ring polymers (chain length $N_R=2 N_L$) is presented. Two distinct off-lattice models are studied, one by Monte Carlo methods, the other by Molecular Dynamics, using a fast implementation on graphics processing units (GPUs). It is shown that the monomer density profiles $\rho(z)$ in the $z$-direction perpendicular to the surface for rings and linear chains are practically identical, $\rho_R(2 N_L, z)=\rho_L(N_L, z)$. The same applies to the pressure, exerted on a piston at hight z, as well. While the gyration radii components of ri…
Insight in NLO Polymer Material Behavior from Langevin Dynamic Modeling of Chromophore Poling
2011
Calculation of chromophore polar order, i.e. the polarization of nonlinear optically (NLO) active polymers poled by external field, is challenging. One possible solution is to reproduce the orientation polarization of chromophores under external field using Langevin dynamics (LD) molecular modeling. The present work investigates the influence of chromophore dipole moment, density and field extent on NLO efficiency and polarization/relaxation dynamics. Results of simulations convince us, that the method is applicable for modeling real NLO polymers. In the spotlight of this investigation we would like to describe a NLO polymer as a “ferrofluid” where chromophores are active particles or elect…
Translocation dynamics of a short polymer driven by an oscillating force
2013
Under the terms of the Creative Commons Attribution 3.0 Unported License.
A coarse-graining procedure for polymer melts applied to 1,4-polybutadiene
2009
We present a coarse-graining procedure for homopolymer melts mapping intra- as well as inter-molecular interactions from a chemically realistic united atom description to a bead-spring type molecular model. On the coarse-grained level the repeat units interact through bond-length and bond angle potentials and a non-bonded Lennard-Jones type interaction. The latter one is of the 7,4 form and softer than the typically employed 12,6 interactions. The coarse-graining of the intramolecular interactions follows well developed procedures, however, we point out in which way the non-bonded intramolecular interactions in the chemically realistic model should be treated. The parameters of the non-bond…
Compressed Polymer Brushes under the Shear Flow
1998
The structure and dynamics of two compressed polymer brushes under the shear deformation were investigated by the methods of stochastic dynamics. The shear was created by the move-ment of grafting planes with the constant velo-cities in opposite directions along the planes.
Selfdiffusion of polymer chains in solutions and melts
2005
Anomalous diffusion of monomers of polymer chains, as well as motion of these chains as a whole, is discussed with an emphasis on Monte Carlo simulations and simple scaling concepts. While the behavior of isolated chains in good solvents or Theta-solvents without excluded volume interactions is fully accounted for by the Rouse model, the behavior is less clear both for isolated chains in bad solvents and for chains in dense melts. Collapsed chains are shown to diffuse as g3(t) = <([rCM (t) -rCM(0)]2〉 ∝ tξ3 where the (effective?) exponent ξ3 simply seems to be linearly temperature-dependent for temperatures T lower than the Σ-temperature, ξ3 T/Θ. A relaxation time τ oc N3 is found, and scali…
Mechanical Properties of Single Molecules and Polymer Aggregates
2013
This chapter deals with the mechanical properties of single polymer chains, aggregates, and supramolecular complexes. The topics discussed cover a broad range from fundamental statistical mechanics of the equilibrium elastic properties of single polymer chains to details of the behavior of binding pockets in biomolecular assemblies as observed by force spectroscopy. The first section treats the equilibrium mechanical properties of single polymer chains in various environments, investigated via extensive simulations employing coarse-grained models that have proven extremely successful in many branches of polymer physics, namely the bond-fluctuation model and the self-avoiding walk model. Apa…
Microscopic verification of dynamic scaling in dilute polymer solutions: A molecular-dynamics simulation
1991
The dynamics of a single polymer chain immersed in a large number of solvent particles is studied by molecular dynamics. This is the first simulation where chain length (30, 40, and 60 monomers) and statistical accuracy are sufficient to test the predictions of the Zimm model as a result of the particle-particle interactions: The short-time diffusion constant is in good agreement with the Kirkwood prediction, and the monomer motions exhibit the expected dynamic scaling. The long-range hydrodynamic interaction requires a data analysis that explicitly includes the periodic images via Ewald sums.
Counterion-mediated attraction and kinks on loops of semiflexible polyelectrolyte bundles.
2006
The formation of kinks in a loop of bundled polyelectrolyte filaments is analyzed in terms of the thermal fluctuations of charge density due to polyvalent counterions adsorbed on the polyelectrolyte filaments. It is found that the counterion-mediated attraction energy of filaments depends on their bending. By consideration of curvature elasticity energy and counterion-mediated attraction between polyelectrolyte filaments, the characteristic width of the kink and the number of kinks per loop is found to be in reasonable agreement with existing experimental data for rings of bundled actin filaments.
Structural properties of concave cylindrical brushes interacting with free chains
2011
We present a self-consistent field theoretical study of the microstructure of concave cylindrical brushes as a function of the cylinder radius, grafting density, grafted chain length, and the solvent quality. We show that the results for the radial monomer density profile and the distribution of the free ends are in good agreement with the corresponding molecular dynamics results. Part of the investigation is focused on the conformational behavior of a free macromolecule in a cylindrical brush. A central result is the observed non-monotonous variation of the size of a free chain in a brush-coated tube when the tube radius is systematically changed. An interpretation of this behavior which d…