Static and dynamic hypersonic properties are probed to reveal the subtle interplay between demixing, matter transport, chemical network formation, polymer network swelling, and network damage in the vicinity of the interface between the reactants of amine-curing epoxies. An innovative time- and space-resolved acoustic microscopy, called scanning Brillouin microscopy, gives access to these competing transport and structure formation processes in epoxy systems consisting of either pure resin, alumina nanoparticles-filled resin, or various epoxy resin-hardener mixtures topped by a layer of pure hardener.