Exploration of the ordered morphologies of thermo- and photo-responsive LCOT block copolymer systems

The microphase separation of block copolymer systems as a function of temperature is generally well understood. However, not all applications are amenable to changes in temperature, and therefore the use of other stimuli to induce changes in the nanostructured behavior of block copolymers is desired. By incorporating small amounts of the photoactive molecule azobenzene into the polymer sidegroups, we have identified a system that exhibits both thermo- and photo-responsive behavior. Upon introduction into imidazolium-based ionic liquid solvents, poly(methyl methacrylate)-b-(benzyl methacrylate-s-4-phenylazophenyl methacrylate) (MBsA, 70 kDa, <10 mol% azobenzene) displays lower critical ordering transition (LCOT) behavior, where microphase separation occurs upon heating, and can be modulated by light. Using small amplitude oscillatory shear rheology and small angle X-ray scattering, we are able to understand the ordering behavior of the system. By irradiating MBsA in situ while probing with these techniques, we can further understand the photo-responsiveness. Here, we explore the ordered phases achieved by MBsA in various ionic liquids, as well as the potential for photo-induced order-order transitions.