No abstract

Epoxy/block copolymer (BCP) blends are highly versatile materials. The BCPs can form nanostructures in the resins that improve the toughness of the thermoset as well as provide a template for nanoparticles. However, to fully unlock their potential, more needs to be understood about how to form and stabilize long-range ordered nanostructures within the unique chemical environment of a cured epoxy matrix. In this work, an ionic liquid (1-ethyl-3-methylimidazolium dicyanamide) was used as both the curing agent and a structure-directing agent in an epoxy/poly­(ethylene oxide-b-propylene oxide-b-ethylene oxide) blend. Small-angle X-ray scattering (SAXS) analysis of the ternary phase space of the epoxy/BCP/ionic liquid blend showed that a wide range of self-assembled structures were attained in the uncured blends using this low-cost BCP, including higher ordered structures such as hexagonally packed cylinders and lamellar structures. Comparisons of the structures before and after epoxy curing showed that many of the compositions undergo phase transitions during the curing process. In situ SAXS showed that these transitions can be quite complex for some compositions. Importantly, it was shown that these phase changes proceed through a variety of transition structures rather than dissolving and reforming the new structures. These findings demonstrate new strategies for imparting long-range order in epoxy/BCP blends through the use of ionic liquid curing agents.