Conditions of rapid processing often drive polymers to adopt nonequilibrium molecular conformations, which, in turn, can give rise to structural, dynamical, and mechanical properties that are significantly different from those in thermodynamic equilibrium. However, despite the possibility to control the desired nonequilibrium properties of polymers, a rigorous microscopic understanding of the processing–property relations is currently lacking. In an attempt to stimulate progress along this topical direction, we focus here on three prototypical and apparently different cases: spin-coated polymer films, rapidly drawn polymer fibers, and sheared polymer melts. Inspired by the presence of common observations in the chosen cases, we search for order parameters as, for example, topological correlations and heterogeneities, which may allow characterizing the processing-induced behavior of polymers. We highlight that such approaches, necessitating concerted efforts from theory, simulations, and experiments, can provide a profound understanding leading to predictable and tunable properties of polymers.

We show that thin film star-shaped macromolecules exhibit significant differences in their average vitrification behavior, in both magnitude and thickness dependence, from their linear analogs. This behavior is dictated by a combination of their functionality and arm length. Additionally, the glass transition temperature at the free surface of a star-shaped molecule film may be higher than that of the interior, in contrast to their linear analogs where the opposite is true. These findings have implications for other properties, due largely to the origins, entropic, of this behavior.

Multi-phase nanostructured polymer electrolytes, where the one phase conducts ions while the other imparts the desired mechanical properties, are currently the most promising candidates for solid-state electrolytes in high-density lithium metal batteries. In contrast to homogeneous polymer electrolytes, where ion transport is coupled with polymer segmental dynamics and any attempt to improve conductivity via faster polymer motions results in a decrease in stiffness, nanostructured materials efficiently decouple these two antagonistic parameters. Nevertheless, for reasons discussed herein the synthesis of a polymer electrolyte that simultaneously has a shear modulus of G′ ≈ GPa and an ion conductivity of σ > 10^–4 S/cm (in the case dual ion conductor) or of σ > 10^–5 S/cm (in the case of single-ion conductor) remains a challenge. This review focuses on recent designing strategies for the synthesis of all-polymer nanostructured electrolytes, and protocols for introducing a single-ion character in such materials.

This study investigates the fundamental influence of cation chemistry on the ionic conductivity of PEO-based electrolytes, with implications for advancing polymer electrolyte design. Two PEO systems─high molecular weight (M_w = 100 kg/mol) and low molecular weight (M_w = 0.35 kg/mol)─were blended with LiTFSI and NaTFSI salts to explore ion transport mechanisms. In the high-M_w PEO, where ion hopping dominates, smaller Li⁺ ions exhibit higher conductivity (σ_LiTFSI > σ_NaTFSI). In contrast, the low-M_w PEO, where ion diffusion is the primary mechanism, shows higher conductivity for larger Na⁺ ions (σ_NaTFSI > σ_LiTFSI). In the former, rheology measurements indicate that larger Na⁺ cations form more transient EO:Na⁺ contact, hindering cation hopping and reducing conductivity. In the latter, the stronger EO:Li⁺ interactions lead to a larger hydrodynamic radius and slower diffusion. Notably, PEO-0.35K:NaTFSI exhibits a room-temperature conductivity of σ_NaTFSI ≈ 4 × 10^-4 S/cm, meeting the requirements for practical applications. These findings highlight the potential of low-M_w PEO and Na-based electrolytes for the development of efficient Na-ion batteries.