21 research outputs found
Adsorption of a semiflexible polymer onto interfaces and surfaces
We consider the adsorption of a semiflexible polymer chain onto interfaces
and surfaces by using the differential equation of the distribution function
of the end-to-end distance , which is associated with the moment
expansion of the latter. We present the results of the approximative treatment
consisting of taking into account the 2nd and 4th moments in the differential
equation for . The essential features of adsorption of the semiflexible
polymer are: {\it i}) the existence of a new local length scale, which results
in two-exponential decay of the monomer density of adsorbed polymer; {\it ii})
the binding of the semiflexible polymer is weaker than that for flexible one
for both interface and wall. The approximative theory presented is restricted
to the regime of weak adsorption, where the effect of the rodlike behavior of
the polymer on small scales is weak.Comment: 9 pages, 2 figure
Adsorption of a random heteropolymer with self-interactions onto an interface
We consider the adsorption of a random heteropolymer onto an interface within
the model by Garel et al. [1] by taking into account self-interactions between
the monomers. Within the replica trick and by using a self-consistent
preaveraging procedure we map the adsorption problem onto the problem of
binding state of a quantum mechanical Hamiltonian. The analysis of the latter
is treated within the variational method based on the 2-nd Legendre transform.
We have found that self-interactions favor the localization. The effect is
intensified with decrease of the temperature. Within a model without taking
into account the repulsive ternary monomer-monomer interactions we predict a
reentrant localization transition for large values of the asymmetry of the
heteropolymer and at low enough temperatures.Comment: 11 pages, 3 figure
Localization of a Gaussian polymer in a weak periodic surface potential disturbed by a single defect
Using the results of the recently studied problem of adsorption of a Gaussian
polymer in a weak periodic surface potential we study the influence of a single
rod like defect on the polymer being localized in the periodic surface
potential. We have found that the polymer will be localized at the defect under
condition u>u_c, where u_c is the localization threshold in the periodic
potential, for any infinitesimal strength of the interaction with defect. We
predict that the concentration of monomers of the localized polymer decays
exponentially as a function of the distance to the defect and is modulated with
the period of the surface potential.Comment: 7 pages, 5 figures, revtex
Polymer drift in a solvent by force acting on one polymer end
We investigate the effect of hydrodynamic interactions on the non-equilibrium
drift dynamics of an ideal flexible polymer pulled by a constant force applied
at one end of the polymer using the perturbation theory and the renormalization
group method. For moderate force, if the polymer elongation is small, the
hydrodynamic interactions are not screened and the velocity and the
longitudinal elongation of the polymer are computed using the renormalization
group method. Both the velocity and elongation are nonlinear functions of the
driving force in this regime. For large elongation we found two regimes. For
large force but finite chain length the hydrodynamic interactions are
screened. For large chain lengths and a finite force the hydrodynamic
interactions are only partially screened, which in three dimensions results in
unusual logarithmic corrections to the velocity and the longitudinal
elongation.Comment: 6 page
Statistical mechanical description of liquid systems in electric field
We formulate the statistical mechanical description of liquid systems for
both polarizable and polar systems in an electric field in the
-ensemble, which is the pendant to the thermodynamic description in
terms of the free energy at constant potential. The contribution of the
electric field to the configurational integral in
the -ensemble is given in an exact form as a factor in the
integrand of . We calculate the contribution of the
electric field to the Ornstein-Zernike formula for the scattering function in
the -ensemble. As an application we determine the field induced
shift of the critical temperature for polarizable and polar liquids, and show
that the shift is upward for polarizable liquids and downward for polar
liquids.Comment: 6 page
Surface segregation of conformationally asymmetric polymer blends
We have generalized the Edwards' method of collective description of dense
polymer systems in terms of effective potentials to polymer blends in the
presence of a surface. With this method we have studied conformationally
asymmetric athermic polymer blends in the presence of a hard wall to the first
order in effective potentials. For polymers with the same gyration radius
but different statistical segment lengths and the excess
concentration of stiffer polymers at the surface is derived as % \delta \rho
_{A}(z=0)\sim (l_{B}^{-2}-l_{A}^{-2}){\ln (}R_{g}^{2}/l_{c}^{2}{)%}, where
is a local length below of which the incompressibility of the polymer
blend is violated. For polymer blends differing only in degrees of
polymerization the shorter polymer enriches the wall.Comment: 11 pages, 7 figures, revtex