(291a) Brownian Dynamics Simulations of Polyelectrolyte Adsorption Onto Charged Patterned Surfaces

The adsorption of a polyelectrolyte molecule onto a surface decorated with nanometer-scale charged patches is studied using Brownian dynamics simulations. The polyelectrolyte molecule is modeled as a uniformly charged freely jointed bead-rod chain and electrostatic interactions are incorporated using a screened Coulombic potential. We explore the effect of various parameters such as patch length, patch periodicity, surface charge density, chain length, and screening length on chain conformation. The simulations predict that the chain lies close to the adsorbing surface if the patch length, surface charge density, and screening length are sufficiently large. It is observed that for certain arrangements of charged patches, the planar component of the radius-of-gyration for an adsorbed chain is smaller that its free solution value, in contrast to what is observed for a uniformly charged surface. We discuss how the arrangement of the charged patches can be adjusted to control chain conformation and mobility. The results of this study will help in nano-engineering surfaces to control polyelectrolyte adsorption, which plays a crucial role in emerging technologies such as layer-by-layer assembly of thin films and microfluidics.