Authors R. Descas, J.-U. Sommer and A. Blumen
Title Dynamical scaling of single chains on adsorbing substrates: Diffusion processes
Date 01.04.2005
Number 111
Abstract We study the dynamics of tethered chains of length N on adsorbing surfaces, considering the dilute case; for this we use the bond fluctuation model and scaling concepts. In particular, we focus on the mean-square displacement of single monomers and of the center of mass of the chains. The characteristic time tau of the fluctuations of a free chain in a good solvent grows as tau~Na, where the coefficient a obeys a=2nu+1. We show that the same coefficient also holds at the critical point of adsorption. At intermediate time scales single monomers show subdiffusive behavior; this concurs with the behavior calculated from scaling arguments based on the dynamical exponent a. In the adsorbed state tau[perpendicular], the time scale for the relaxation in the direction perpendicular to the surface, becomes independent of N; tau[perpendicular] is then the relaxation time of an adsorption blob. In the direction parallel to the surface the motion is similar to that of a two-dimensional chain and is controlled by a time scale given by tau||~N2nu2+1L–2Deltanu/nu, where nu2 is the Flory exponent in two dimensions, nu is the Flory exponent in three dimensions, and Deltanu=nu2–nu. For the motion parallel to the surface we find dynamical scaling over a range of about four decades in time.
Publisher Journal of Chemical Physics
Citation Journal of Chemical Physics 122 (2005) 134903-134913

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