As their interactions have, to a good approximation, no energetic component, purely repulsive particles were used to determine the contribution of entropy to molecular alignment at the solid and vapour interfaces. For these purely repulsive particles, the shape parameters described above (with κ = 0.30, 0.35, 0.40, 0.45, 0.50) were used, and κ was fixed at 0.2 (ε S = 1, ε F = 5). The GB potential was cut-off and shifted to 0 at the minimum for each orientation to obtain a purely repulsive potential, analogous to the Weeks-Chandler-Andersen (WCA) truncation of the LJ potential. Likewise, a cut-off and shifted form of the fluid-substrate interactions, using the mixing rules for combining GB parameters of two dissimilar particles discussed previously, was used for the interactions with the solid substrate. These simulations were conducted at T = 0.62ε/k B at overall volume fractions between 0.1 and 0.5 using either the silicon or graphene substrate. Although these systems are expected to be athermal, simulations were also carried out for the silicon substrate at T = 0.8ε/k B to verify this fact. A full list of the systems studied is given in ESI Table . Data for the different substrates and temperatures was combined to determine the scaling of interface orientation with system parameters (see ESI, section S4).