SESANS study of a UV light-induced phase transition in diarylethene derivative assemblies

We propose a SESANS experiment to gain insight on a structural change that occurs in an aggregated system of photo-switchable molecules similar to those recently studied in beamtime session RB2220130. Here, when the moiety is "open", a solid assembly of polyhedra result, with tuneable size in the region 1-10 μm, while when "closed" by the application of UV light, a change to a visibly more liquid (amorphous) state occurs. Various data have been collected on this system already, including SAXS (below) but the assemblies themselves and much of their internal structure are too large to be resolved by that technique. Light microscopy shows the bulk changes at larger length scales, but no information on the nanoscale. SESANS on LARMOR is required to access the range of length-scales necessary to build up a detailed structural picture of this transition and of the systems before and after the measurement.