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  4. Maximizing ion conduction in single-ion-conducting ionomers is essential for their application in energy-related technologies such as Li-ion batteries. Understanding the anion chemical composition impacts on ion conduction offers new perspectives to maximize ion transport, since the current approach of lowering T g has apparently reached a limit (lowest T g ∼ 190 K, highest conductivity ∼10 −5 –10 −4 S cm −1 ). Here, a series of random ionomers are synthesized by copolymerizing poly(ethylene glycol)methacrylate with either sulfonylimide lithium methacrylate (MTLi) or sulfonate lithium methacrylate (MSLi) using reversible addition–fragmentation chain transfer (RAFT) polymerization. Li-Ion conduction and self-diffusion coefficients ( D Li + ) of the ionomers are characterized with dielectric relaxation spectroscopy (DRS) and pulsed-field-gradient (PFG) NMR diffusometry, respectively. Increasing ion content decreases the Li-ion conductivity and D Li + , as expected from the increased T g . Moreover, a considerably lower ionic conductivity and D Li + are observed for MSLi compared to MTLi at constant ion content and T g / T . As revealed from X-ray scattering, strong ion aggregation in MSLi results in much lower conductivity and D Li + compared with less aggregated MTLi based on the more delocalized sulfonylimide anion. These results emphasize the detrimental and molecularly specific role of ion aggregation in Li-ion conductivity, and highlight the necessity for minimizing ion aggregation via the rational choice of anion chemical composition. 
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  5. Molecular ionic composites (MICs) are a new class of solid electrolytes that combine ionic liquids (ILs) and a rigid-rod double helical polyelectrolyte, poly(2,2′-disulfonyl-4,4′benzidine terephthalamide) (PBDT). In this study, we focus on the mechanical, dielectric, and ion diffusive dynamics of MICs with a fixed PBDT weight percent (10 wt%) and varying IL chemistry and molecular volume ( V m ). All six MICs produce tensile moduli in the range of 50–500 MPa at 30 °C, up to 60× higher than the shear moduli of the same MICs. The high range of moduli and tensile to shear modulus ratio emphasizes that the distribution of PBDT chains and the strong ionic interactions between IL ions and PBDT chains dictate the modulus and the mechanical strength in MICs. Additionally, these MICs exhibit high ionic conductivities ranging from 1–6 mS cm −1 at 30 °C, consistent with the measured diffusion coefficients of the IL ions. The tunability of the extraordinary mechanical properties and high ionic conductivities of MIC electrolytes greatly inspire their use in advanced electrochemical devices. 
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