Self-assembling network and bundle structures in systems of rods and crosslinkers - A Monte Carlo study

Self-assembling structures are studied in a binary system of long and short spherocylinders. The short spherocylinders have an adhesive site on both ends with which they can bind to the long spherocylinders. In this way, they act as crosslinkers that may interconnect a pair of long rods. With the help of Monte Carlo simulations, the structure of crosslinker-mediated rod assemblies is studied as a function of rod and crosslinker concentrations, and of the adhesive strength between the two. Though the system is rather simple compared to networks of crosslinked filaments in the cytoskeleton, it shows a complex phase behaviour, including the formation of bundles of parallel rods and a transition to a three-dimensional, low-density network. These bundles occur both in percolated and non-percolated systems. In a certain range of rod and crosslinker concentrations, the amount of bundling rods is a non-monotonic function of the adhesive strength. The percolation boundary has been determined and the dependence of bundle formation on the system parameters has been studied systematically.