We use a steepest descent algorithm to optimize the single chains. We also allow the simulation box to relax in the periodic direction of the chains. In the other two directions, we set the box length to 40 Å to ensure a large distance between the periodic images of the chains. The aggregation process is explored using temperature annealing followed by an equilibrium simulation for a total period of 10 ns. To enhance the conformational sampling, the runs are started at an artificially high temperature of 1500 K and are then cooled down to 300 K (cooling rate of 0.12 K/ps). A time step of 1 fs is used in all simulations. The initial systems of N = 100 chains were set in orthogonal boxes, and during the run, we only applied the barostat to the b-direction of the box. After the initial NPT simulations, we take out representative subsets from the center of the resulting clusters to prepare another set of simulation cells. These systems are again equilibrated in an NPT ensemble simulation for 5 ns at T = 300 K. This time, we apply the barostat to all dimensions, and we also allow the simulation boxes to adopt a triclinic shape.