Synthesis of Asymmetric Bottlebrush Random Copolymers and Their Assembly in the Bulk and at Fluid Interfaces

Block copolymers are widely used to access ordered nanostructures, but creating highly asymmetric lamellae remains challenging. This difficulty arises because interfacial energetics and chain-stretching penalties are inherently coupled in conventional linear architectures, where interfacial area and chain conformation cannot be tuned independently. To address this limitation, we synthesized a systematic library of polyethylene oxide (PEO)- and polydimethylsiloxane (PDMS)-grafted bottlebrush random copolymers (BRCPs) via ring-opening metathesis polymerization, in which the backbone degree of polymerization and side-chain asymmetry were independently varied to program molecular architecture. Small-angle and wide-angle x-ray scattering revealed that longer PDMS side chains suppressed the crystallization of shorter PEO chains and drove a systematic increase in lamellar spacing. Confinement imposed by the bottlebrush backbone further promoted the formation of highly asymmetric lamellar morphologies even at pronounced compositional asymmetries. Motivated by these results in the solid state, we additionally examined the fluid-fluid interfacial behavior of these BRCPs, finding that side-chain length governs interfacial tension and that architectural asymmetry and chain mobility enable spontaneous emulsification through Marangoni-driven instabilities. Overall, these findings contribute molecular-level design rules governing crystallization and lamellar organization in the solid state, as well as principles for engineering tailored emulsifiers and dynamic interfacial materials.