Simulation of the Dynamics of Surface-Tethered Linear, Helical, and Bottlebrush Polymers

Polymer brushes are an important class of materials that find uses in a wide range of applications (such as in tuning immune responses to new therapeutics) and computer simulations play a key role in interpreting the behavior of grafted polymers. Understanding the details of polymer dynamics, in general, can be done through mode analysis in particle-based simulations. For instance, Rouse mode analysis transforms the coordinates of monomers into a set of normal coordinates using a cosine basis, after which the relaxation times of each mode can be computed by observing the decay of the normal mode autocorrelation function with time. Although this approach is applicable to studying the dynamics of a variety of polymer systems, the cosine basis may not always be applicable to a particular architecture or grafting condition, and use of an inapplicable basis can complicate interpretation of dynamical behaviors. Here, we demonstrate the use of proper orthogonal decomposition (POD) to compute the relaxation modes of a variety of polymer architectures when tethered to a surface, and demonstrate quantitative agreements with neutron scattering measurements of similar systems – enabling us to better interpret the dynamics of more complicated polymer architectures.