Adsorption Transition of a Polymer Chain at a Weakly Attractive Surface: Monte Carlo Simulation of Off-Lattice Models

A bead-spring model of a polymer chain with one end attached to a wall is studied by Monte Carlo simulations for chain lengths 16 ≤ N ≤ 256. Two types of adsorption potentials, 9-3 and 10-4 Lennard-Jones (LJ) potentials, between the effective monomers and the wall are assumed. For both cases the adsorption transition where the chain changes its asymptotic statistical properties from a three-dimensional to a two-dimensional configuration is located using a scaling analysis. It is shown that the crossover exponent φ = 0.50 ± 0.02 is the same for both LJ potentials. This value is compatible with recent theoretical predictions and simulation results for lattice models with short-range wall potentials. The results of our study support the expectation that the exponents describing the adsorption transition are universal, i.e., they are not influenced by the precise form and the long-range character of the adsorption potentials used. The technical aspects of the simulations (which use configurational bias methods as well as histogram re-weighting) are also carefully discussed. Snapshot pictures of a bead-spring model of a polymer chain with N = 256 beads with one end anchored on the surface: (a)“mushroom configuration”, (b) εa ≈ εw at the adsorption transition, and (c)“pancake configuration” of a strongly adsorbed chain.