Control of nanostructures generated in epoxy matrices blended with PMMA-b-PnBA-b-PMMA triblock copolymers

Stability of nanostructures of epoxy/acrylic triblock copolymer blends was studied. PMMA-b-PnBA-b-PMMA triblock copolymers (acrylic BCPs) having several compositions on the ratio of the block chains and the molecular weight were initially prepared and were blended with diglycidyl ether of bisphenol-A epoxy thermosets. The blends were cured using phenol novolac with tri phenyl phosphine (TPP) as the catalyst. Several nanostructures, such as spheres, cylinders, curved lamellae, were observed in the cured blends. The nanostructures were controlled by the molecular weight of the immiscible PnBA-block chain and the ratio of the PnBA in the blends. Moreover, the effect of the gel time to the nanostructures was examined by altering the trace amount of the TPP in the blends. The types of the nanostructures were almost kept irrespective of the gel time of the blends when the composition of the blends was maintained. This suggested the stability of the nanostructures of the epoxy/acrylic BCP blends made via the self-assembly mechanism, therefore a phase diagram of the cured blends was proposed.