Order-to-order transitions in architecturally asymmetric linear-block-bottlebrush copolymers using ionic liquids as selective solvents.

Microphase separated block copolymers (BCPs) form technologically useful 3D networks (NETs) that find applications arising from their bicontinuous nature which enables orthogonal tunability of the properties of each domain, e.g., mechanically tough yet highly ion conductive materials. However, the the phase space over which NETs stably form is limited to small composition windows due in large part to the packing frustration associated with the nodes connecting NETs. Here, we explore how the addition of block selective solvents to an architecturally asymmetric linear-block-bottlebrush BCP induces order-to-order transitions. Six different ionic liquids with varying alkyl chain lengths are used in order to control the selectivity of the solvent for the minority linear segments. In situ small angle X-ray scattering is used to characterize the solvent-induced order-to-order transitions and to quantify the solvent selectivity. We show that the addition of ionic liquid allows for the formation of a variety of coexisting morphologies regardless of the selectivity of the solvent.