Computer Simulation Of Wormlike Chain And Polyelectrolyte Polymer

Most biological molecules are more appropriately described by a semi-flexible chain model and polyelectrolyte, i.e. DNA, protein etc.. The work presents computer simulation of wormlike polymer and polyelectrolyte system using self-consistent mean field theory (SCFT) and Dissipative Particle Dynamics (DPD) methods. First, to go beyond the widely used Gaussian chain model, a wormlike chain model based self-consistent mean field theory as well as numerical method (including finite difference method and spectral method) are developed. And In order to capture the long-range electrostatic interactions in the polyelectrolyte system efficiently, we couple the non-homogenous Poisson equation into Dissipative Particle Dynamics method, and by max-imum the energy functional of the electrostatic field with an iterative method, we can obtain the electrostatic field efficiently.First, We investigate a homopolymer brush system on the basis of the wormlike chain model, incorporating an Onsager-type interaction between polymer segments in the excluded-volume interaction. Our numerical solutions to the self-consistent field theory are compared with scaling properties that can be deduced in various limits. We then consider the adsorption of a semi-flexible wormlike polymer to the surface of a flat wall by a square potential well of width W and depth v. For a wormlike chain much longer than the persistence length, we numerically calculate the adsorption phase diagram and analyze the scaling behavior near the phase transition. Our numerical results over a wide range of W can be used to identify scaling behaviors valid in the large and small width-to-persistence-length ratio as well as near the adsorption phase transition.The conformational behaviors of charged brushes on a micelle self-assembled by charged-neutral diblock copolymers in salt-free solution are extensively analyzed using a coarse-grained dissipative particle dynamic simulation. When only monovalent coun-terions exist, the brush conformation of the corona in the micelle is exactly consistent with the predictions from the blob-scaling theory based on the spherical polyelectrolyte brush model. However, for multivalent counterions such as divalence and trivalence, the strong electrostatic correlations lead the micelle structures to deviate obviously from those of scaling predictions. The collapse of the brush appears to be due to the drop in the osmotic pressure inside the corona region of the micelle. The multi-functional role of the glycocalyx layer, coating the luminal surface of blood vessels, has been well recognized. Here, we consider microchannel flows and develop scaling laws governing the height of the glycocalyx and the velocity slip at its surface as a function of the pressure drop as well as the grafting density of glycocalyx fibers and their stiffness. We combine3D dissipative particle dynamics simulations and mean field theory to obtain general expressions, assuming a homogeneous flow that ignores the discrete effects of blood cells. Surprisingly, we find that at low Reynolds number the slip length decreases with the mean flow velocity unlike the behavior of polymer brushes where the slip length remains constant.