3,275 research outputs found
Sterically stabilized lock and key colloids: A self-consistent field theory study
A self-consistent field theory study of lock and key type interactions
between sterically stabilized colloids in polymer solution is performed. Both
the key particle and the lock cavity are assumed to have cylindrical shape, and
their surfaces are uniformly grafted with polymer chains. The lock-key
potential of mean force is computed for various model parameters, such as
length of free and grafted chains, lock and key size matching, free chain
volume fraction, grafting density, and various enthalpic interactions present
in the system. The lock-key interaction is found to be highly tunable, which is
important in the rapidly developing field of particle self-assembly
Star Polymers Confined in a Nanoslit: A Simulation Test of Scaling and Self-Consistent Field Theories
The free energy cost of confining a star polymer where flexible polymer
chains containing monomeric units are tethered to a central unit in a slit
with two parallel repulsive walls a distance apart is considered, for good
solvent conditions. Also the parallel and perpendicular components of the
gyration radius of the star polymer, and the monomer density profile across the
slit are obtained. Theoretical descriptions via Flory theory and scaling
treatments are outlined, and compared to numerical self-consistent field
calculations (applying the Scheutjens-Fleer lattice theory) and to Molecular
Dynamics results for a bead-spring model. It is shown that Flory theory and
self-consistent field (SCF) theory yield the correct scaling of the parallel
linear dimension of the star with , and , but cannot be used for
estimating the free energy cost reliably. We demonstrate that the same problem
occurs already for the confinement of chains in cylindrical tubes. We also
briefly discuss the problem of a free or grafted star polymer interacting with
a single wall, and show that the dependence of confining force on the
functionality of the star is different for a star confined in a nanoslit and a
star interacting with a single wall, which is due to the absence of a symmetry
plane in the latter case.Comment: 15 pages, 9 figures, LaTeX, to appear in Soft Matte
Hydrophobic interactions with coarse-grained model for water
Integral equation theory is applied to a coarse-grained model of water to
study potential of mean force between hydrophobic solutes. Theory is shown to
be in good agreement with the available simulation data for methane-methane and
fullerene-fullerene potential of mean force in water; the potential of mean
force is also decomposed into its entropic and enthalpic contributions. Mode
coupling theory is employed to compute self-diffusion coefficient of water, as
well as diffusion coefficient of a dilute hydrophobic solute; good agreement
with molecular dynamics simulation results is found
Controlling the Interactions between Soft Colloids via Surface Adsorption
By employing monomer-resolved computer simulations and analytical
considerations based on polymer scaling theory, we analyze the conformations
and interactions of multiarm star polymers strongly adsorbed on a smooth,
two-dimensional plane. We find a stronger stretching of the arms as well as a
stronger repulsive, effective interaction than in the three dimensional case.
In particular, the star size scales with the number of arms as and the effective interaction as , as opposed to and , respectively, in three dimensions. Our results
demonstrate the dramatic effect that geometric confinement can have on the
effective interactions and the subsequent correlations of soft colloids in
general, for which the conformation can be altered as a result of geometrical
constraints imposed on them.Comment: 17 pages, LaTeX, 5 figures, to appear in Macromolecule
Covariant Treatment of Neutrino Spin (Flavour) Conversion in Matter under the Influence of Electromagnetic Fields
Within the recently proposed Lorentz invariant formalism for description of
neutrino spin evolution in presence of an arbitrary electromagnetic fields
effects of matter motion and polarization are considered.Comment: Extended version of contribution to "Particle Physics on Boundary of
Millenniums" (Proceedings of the 9th Lomonosov Conference on Elementary
Particle Physics, World Scientific, Singapure
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