On the interplay between matter transport and structure formation at epoxy–hardener interfaces visualized by scanning Brillouin microscopy

Abstract

Structural developments are investigated in network-forming reactive polymers by time- and space-resolved scanning Brillouin microscopy. Hypersonic properties are probed to reveal the subtle interplay between molecular transport, dissolution, polymerization and network defects in the vicinity of the interface between reactants, which are either pure epoxy resin or various epoxy resin–hardener mixtures, topped by a layer of pure hardener. The trans-interfacial polymerization produces heterogeneous epoxy structures of either gelatinous or glassy nature. Interestingly, the hardener can easily penetrate and swell these networks and epoxy network fragments can be transported over several millimetres by convective flow. The observed features may be used to form interpenetrating networks during self-healing procedures.