Each simulated system consisted of a cubic cell filled with a stoichiometric mixture of 2000 DGEBA and 1000 DDS molecules, for a total of 127,000 atoms. In order to investigate finite-size effects, we additionally constructed a set of smaller cells, comprising 100 DGEBA, 50 DDS molecules (6,350 atoms) and 500 DGEBA, 250 DDS molecules (31,750 atoms), respectively. The amorphous starting structures were assembled with Packmol, 47 at a density of 1 g / cm . The smallest inter-atomic distance between two atoms belonging to different molecules was constrained to be greater than 2.5 Å to avoid occasional ring spearing (see Figure for an example). The initial box length was close to 115 Å for the large systems, 73 Å for the intermediate systems and 43 Å for the smaller cells. The AMBERTOOLS17 package was used to output the topology and coordinate files for the five systems. Translation into a LAMMPS (Dec. 2018, stable) data file was then performed by an inhouse conversion script.