Coarse grained modeling of polymers

By Arjen Berkenbos

Polymers are very long molecules, consisting out of many repeating units called monomers. One can change the chemical properties of the monomers, and thus of the polymers, almost at will. This makes polymeric systems very atractive for industrial purposes. In an ideal world one would be able to predict the properties of a polymer chain using computer simulations. Unfortunately this is not possible because polymers are too big to do so. We try to construct coarse-grained polymer models to overcome this problem.

We use a so-called bead-spring model consisting out of a relatively small number of beads (typically less than a hundred) connected by a harmonic potential. Using such a simple model we loose all chemical information about the original polymer. However, by fixing the size of the beads relative to the spring we are able to correctly capture the size and hydrodynamic properties of the original polymer chain. Using this simple polymer model we are able to succesfully reproduce the behaviour of a dilute polymer solution flowing through microfluidic capillaries.

Obviously this model only is valid close to the theta-point, where there effectively are no interactions between the beads. If one wants to construct a model that is also valid away from the theta-point, a potential between all monomers should be included. Currently we are trying to construct such a potential.