Mesoscopic Model with Vectorial Structure Parameter for Star Polymers*

In a previous study on non-equilibrium interactions between star polymers (Briels et al., JCP, 134, 124901, (2011)), we presented a mesoscopic model to describe transient forces where one star polymer is fixed at the origin and the other star polymer is dragged past at a constant velocity. When the moving star is directly above the fixed star, the force along x-direction is zero, in disagreement with small-scale simulations (Singh et al., PRL, 107, 158301, (2011)).

Motivated by this disparity, we present an updated mesoscopic model for transient forces between two star polymers (Fitzgerald and Briels (2017)). Calculation of the transient forces is based on the response of a vectorial structure parameter rather than a scalar parameter, thus allowing for the description of both mixing and deformation processes. This simple model that takes these processes into account turns out to fit into an obvious generalisation of the coarse-grained RaPiD model introduced by us some time ago. The model reproduces forces from the simulation quite well, and at the same time removes an unphysical feature of the RaPiD model used so far.