Forming ordered structures in ternary, photosensitive blends through the use of masks

Using computational modeling, we present a facile method for creating defect-free, spatially periodic structures in immiscible, ternary ABC blends. The approach harnesses a photosensitive, reversible inter-conversion reaction between the A and B components; we specifically focus on cases where the rate of the forward reaction is higher than the reverse reaction. We also utilize a photomask that contains a regular arrangement of holes. When a film of the ternary blend is irradiated through the mask, the C component diffuses to the holes and becomes pinned in these regions. For certain blend compositions, the film forms a defect-free structure that replicates the pattern of the overlying mask. With the removal of the mask, the whole sample becomes uniformly irradiated and the photo-activity of the AB blend drives the mixture to self-assemble into a complex periodic pattern. Thus, the use of one mask permits the creation of multiple ordered morphologies, which can be locked into the film by quenching the system at the appropriate time. The findings reveal that the ordering is controlled by the reaction rate coefficients, the overall composition of the mixture and initial conditions.