Simulation study on the coil-globule transition of adsorbed polymers

Coil-globule transition in two-dimensional polymer chains in an explicit solvent

The structure of two-dimensional polymer chains in a solvent at different temperatures is still far from being fully understood. Computer simulations of high-density macromolecular systems require the use of appropriate algorithms, and therefore the simulations were carried out using the Cooperative Motion Algorithm. The polymer model studied was exactly two-dimensional, coarse-grained and based on a triangular lattice. The theta temperature and temperature of coil-to-globule transition, and critical exponents were determined. The differences between the structure of such a disk and that of a chain in a dense polymer liquid were shown.

Simulation study on the critical adsorption and diffusion of polymer chains on heterogeneous surfaces with random adsorption sites

The critical adsorption and diffusion of a linear polymer chain on a heterogeneous surface with randomly distributed adsorption sites are studied using dynamic Monte Carlo simulations. Results show that the critical fraction of the adsorption sites at which critical adsorption takes place decreases exponentially with the increasing polymer-surface attraction strength and, at the same time, decreases with the increasing intra-polymer attraction strength. For adsorbed polymers with large intra-polymer attraction strength, we also find an adsorption-induced structural transition from a three-dimensional compact globule to a two-dimensional compacted pancake with an increasing fraction of adsorption sites. Anomalous sub-diffusion is observed for the adsorbed polymer diffusion on heterogeneous surfaces, in contrast to the normal diffusion on a homogeneous surface. The polymer on heterogeneous surfaces shows larger fluctuation in the total surface attraction energy and a longer waiting time.

Coarse-grained simulation studies on the adsorption of polyelectrolyte complexes upon lipid membranes

Conformations of a polyelectrolyte complex irreversibly bound to a zwitterionic lipid bilayer.

Dynamics of adsorbed polymers on attractive homogeneous surfaces

Dynamic behaviors of polymer chains adsorbed on an attractive, homogeneous surface are studied by using dynamic Monte Carlo simulations. The translational diffusion coefficient D_xy parallel to the surface decreases as the intra-polymer attraction strength E_PP or the polymer-surface attraction strength E_PS increases. The rotational relaxation time τ_R increases with E_PS, but the dependence of τ_R on E_PP is dependent on the adsorption state of the polymer. We find that τ_R decreases with increasing E_PP for a partially adsorbed polymer but it increases with E_PP for a fully adsorbed polymer. Scaling relations D_xy ~ N^−α and τ_R ~ N^β are found for long polymers. The scaling exponent α is independent of E_PS for long polymers but increases with E_PP from α = 1.06 at E_PP = 0. While β ≈ 2.7 is also roughly independent of E_PS for the adsorbed polymer at E_PP = 0, but β increases with E_PS at E_PP > 0. Moreover, we find that β always decreases with increasing E_PP. Our results reveal different effects of the attractive surface on the diffusion and rotation of adsorbed polymers.