Activation of Ostwald ripening and electrical conductivity in polyHIPEs through the addition of ascorbic acid to graphene-stabilized emulsions

Abstract

Ascorbic acid was employed to increase the sphere-to-sphere contact of polyHIPEs. Adding a radical inhibitor to the aqueous phase of a graphene-stabilized water-in-oil emulsion was hypothesized to delay the formation of a polymer skin around the dispersed droplet, leading to intimate contact between the surfactant-stabilized drops. Optical microscopy analysis of samples made with varying ascorbic acid concentrations showed decreased sphere size and increased size dispersity at increasing inhibitor concentrations. Electrical conductivity measurements showed an increase at low concentrations of ascorbic acid but a decrease in conductivity at higher concentrations. Our results suggest that the presence of an inhibitor does delay the formation of the polymer skin and allows more intimate contact between spheres, but at higher concentrations, it leads to Ostwald ripening. Scanning electron microscopy of polystyrene/graphene composites revealed that the inhibitor also stopped the polymerization of aqueous-dispersed monomer, leading to polymer patches on the interior of the spheres.