(452d) Investigating the Role of Polymer Architecture and Interfacial Mixing on Ion Transport in Linear-Brush Block Copolymer Electrolytes

Polyether-based block copolymers, composed of multiple blocks that self-assemble into phase-separated nanostructures, have significant potential as solid polymer electrolytes for lithium-ion batteries due to the ability to independently tune each block to provide multiple desirable thermal, mechanical, and electrochemical properties to the resulting material. Previous experimental and simulation studies have focused on linear-linear polyether-based block copolymer electrolytes, specifically as PS-PEO/LiTFSI, and found that ionic conductivity heavily relies on segregation strength and that disruption of solvation site connectivity, resulting from interfacial mixing of PS with PEO, is a more plausible explanation for the lower conductivity typically observed near the domain interface, rather than differences in glass transition temperature between blocks [1]. However, a more comprehensive understanding of the relationship between polymer architecture, interfacial mixing, and ion conduction is still lacking. In this study, we investigate the effect of polymer architecture and interfacial mixing on ion transport in linear-brush block copolymer electrolytes, as a function of the side-chain length of the brush block. To accomplish this, we synthesized a series of lamellar-forming diblock copolymers electrolytes, specifically poly(trifluoroethyl methacrylate)-b-poly(ethylene glycol methyl ether methacrylate) (PTFEMA-b-POEM)/LiTFSI to explore the impact of the branched architecture on ionic conductivity. We further characterized these block copolymers using impedance spectroscopy, vibrational spectroscopy, differential scanning calorimetry, and soft X-ray reflectivity to assess and compare the ionic conductivity, degree of dissociation, polymer dynamics, and interface characteristics of the materials. Additionally, we performed molecular dynamic simulations to gain insights into the mechanisms and barriers to ion transport near the domain interface at the molecular level. Overall, our findings suggest that polymer architecture and interface characteristics play a significant role in determining conductivity in these systems.