Thermal Properties and Ion Redistribution in Nanostructured Single-Ion Polymer Electrolyte Blends Composed of Polyanionic Miktoarm Stars

Nanostructured single-ion polymer electrolytes offer a promising strategy to decouple ionic transport from mechanical constraints, yet how nanoscale morphology governs ion partitioning and transport remains poorly understood. Here, we investigate single-ion polymer blend electrolytes composed of polyanionic miktoarm star particles dispersed in a low-molecular-weight poly(ethylene oxide) (PEO) matrix. Differential scanning calorimetry reveals composition-dependent crystallization behavior that provides insight into the distribution of Li+ ions between the polyanionic particles and the oligomeric PEO phase, while polarized optical microscopy resolves the spatial organization of crystalline domains. Glass-transition analysis identifies two regimes separated at approximately 55 wt % particle loading. At high particle contents, Li+ ions remain coordinated within star-rich domains, suppressing crystallization and yielding elevated Tg values. At lower particle contents, formation of a continuous low-molecular-weight PEO phase coincides with a change in Tg behavior, indicating redistribution of Li+ ions toward the unentangled PEO matrix. Temperature-dependent ionic conductivity measurements reveal a transition in ion transport: below 55 wt % particle loading, activation energies comparable to PEO-LiTFSI reference systems indicate Li+ transport dominated by vehicular diffusion in the continuous oligomeric PEO phase, whereas higher activation barriers reflect confined transport governed by ion hopping within star-rich domains. A modified Fox framework accounting for the dependence of Tg on effective lithium-ion concentration captures the Tg behavior across the composition range. These results show that thermal and transport signatures provide complementary evidence of morphology-driven ion partitioning and establish design principles for fast ion transport in nanostructured single-ion polymer electrolytes.