Equilibrium dynamics of a polymer chain end-attached to an adsorbing surface

Abstract

In this thesis we investigate the problem of a single polymer chain one-end grafted to a surface of adjustable attraction strength. Particularly we introduce a locally defined adsorption order parameter and analyze its spatial and temporal correlations to check the consistency of the "blob" picture. We first check the accuracy of our molecular dynamics simulations by reproducing known results pertaining to mean number of adsorbed monomers M, mean height of the chain's free end Z_end, and mean parallel-to-surface component of the chain's gyration radius R_Gpar. We then characterize the scaling of the system in the adsorption regime, finding dynamic dependencies such as t_Zend ~ Zend^3.67, t_RGpar ~ Zend^-0.5, and t_Zend / t_M to hold very well against predictions of scaling theory in conjunction with Rouse model dynamics. The relation between Zend taken as a measure of the adsorption blob size, and the correlation length measured along the chain contour did not take the expected form. Finally, the ratio of the adsorption relaxation time of individual monomers to the global relaxation time, t_mi=t_M was analyzed as a function of the adsorption strength. For large enough N, it shows a sharp drop at the transition point, but both relaxation times scale with N in the same way irrespective of the adsorption regime.