At the nanoscale, weak van der Waals, magnetic, or capillary forces between adjacent ligands and NCs define the cohesion within the SPs. Following our previous studies, we apply a thermally activated crosslinking approach to enhance the NC-NC cohesion within the SPs. When the NPs' surface ligands are crosslinked, these interfaces are dominated by covalent bonds between neighbouring ligands, increasing the overall strength and stiffness of the supraparticles. At the 2nd hierarchical level, the interface between the secondary building blocks (i.e. the SPs) and the polymer phase also provides interfaces that can be adjusted for an increased material's cohesion. The surface of the SPs is, thus, modified by introducing phosphate-derived amine ligands. The phosphate anchoring groups strongly bind to the SPs surfaces, while the amine groups act as chemical anchor points for the epoxy matrix (acc. to Fig. ).