Investigation of Monomer Segment and Salt Distributions in Self-Assembled, Tapered Block Polymer Electrolytes

Tapered block polymers (TBPs) contain modified monomer segment distributions (e.g., gradient or random copolymer regions) at the junction between two homogeneous blocks. Nanostructured polystyrene-block-poly(oligo-oxyethylene methacrylate) TBP electrolytes recently have been shown to exhibit improved ionic conductivities, shear moduli, and processibilities in comparison to their conventional block polymer analogues; however, the microscopic characteristics of TBPs that impart these enhanced properties are unknown. We are studying the nanoscale distribution of monomer segments and lithium salts in normal-, inverse-, and random-tapered TBPs via X-ray and neutron reflectivity, and we are correlating these distributions to the ionic conductivity (via AC impedance spectroscopy) and glass transition temperature (via differential scanning calorimetry) of the materials. By probing the effects of the tapered architecture on ion transport, we can guide the rational design of higher-performance polymer electrolytes.