Self-assembly of Salt-Doped Ternary Polymer Blends

Ternary polymer blends comprising A and B homopolymers and an A-B block copolymer can self-assemble into various microstructures, depending on the polymer composition, chain architecture and temperature. When doped with salt, such blends are promising for applications such as lithium ion batteries due to the tunable morphology. The addition of lithium bis(trifluoromethane)sulfonamide (LiTFSI) to a polymer blend system containing low molar mass poly(ethylene oxide) (PEO) and polystyrene (PS) homopolymers, and a PS−PEO block copolymer (SEO) induces either macroscopic or microscopic phase separation. Blends with different total homopolymer compositions (fH) and volume ratios of PEO and PS homopolymer (fPEO/fPS) at specific temperatures are investigated. In some regions of the phase prism, addition of salt recovers the microphase separated structures of conventional ternary blends, and in particular creates a wide bicontinuous microemulsion (BμE) channel. With still higher fH, a surprising C15 Laves phase is found. This work will help understand the self-assembly of ion-containing A/B/A-B ternary polymer blends and guide the experimental design of polyelectrolyte systems with tunable nanostructures.