We have investigated a new means to control the morphology and conductivity of block copolymer electrolytes by the inclusion of ionic units at the chain ends. A set of poly(styrene-b-ethylene oxide) (PS-b-PEO) block copolymers having dissimilar PEO end groups (−OH, −SO3H, and −SO3Li) exhibited various self-assembled morphologies including disordered, lamellar, and hexagonal cylindrical phases. Strikingly, the addition of Li salts to PS-b-PEO with sulfonate terminal groups afforded enriched nanostructures with significant differences in their conductivities depending on the salt concentration. In particular, a gyroid morphology with a 2-fold-enhanced normalized ionic conductivity was found for the sulfonate-terminated PS-b-PEO when compared to disordered PS-b-PEO-OH. This is closely related to the structural advantages of gyroid having cocontinuous ionic channels, which enable efficient transport of Li+ ions via less tortuous ion conduction pathways. This work presents fascinating experimental insights on the enhancement of ion transport efficiencies by modulating the self-assembly nature of polymer electrolytes by substituting with a single end-functional group.

We present a facile synthetic route toward binder-free, highly-dispersed Ge nanoparticles in carbon matrices using one-step pyrolysis of self-assembled Ge-polymer hybrids. 3-Dimensionally arranged Ge-carbon exhibits remarkably enhanced cycling properties and rate capability compared with carbon sheathed Ge lacking organization.

We have developed fast responsive, colorimetric and resistive-type polymeric humidity sensors from a series of self-assembled poly(styrenesulfonate-methylbutylene) (PSS-b-PMB) block copolymers with tailored hygroscopic properties. In dry state, the PSS-b-PMB films exhibit hexagonal cylindrical morphology where hydrophobic PMB cylinders are dispersed within a PSS matrix. Under levels of humidity, the PSS-b-PMB thin films self-displayed discernible reflective color changes, covering almost entire visible light regions from violet (RH = 20%) to red (RH = 95%). The sensors also revealed a few orders of magnitude changes in impedance with exposure to humid air by taking advantages of strong polymer electrolytes characteristics. Remarkably, the time to complete the changes in the signals was only a few seconds, as rationalized by good connectivity of the PSS domains and short water diffusion pathways in nanometer scales. Repeated hydration/dehydration tests demonstrated reliable sensor properties, which is in sharp contrast to the poor stability of PSS homopolymer sensors lacking organization.

Ion transport properties of block copolymers with lamellar morphologies, which contain ionic liquids (ILs), were investigated. By varying the type of anion in the ILs, dissimilar substructures of lamellar microdomains were identified using different elastic scattering techniques. By decoupling the segmental motion of polymer chains from conductivity, a wide range of normalized conductivities from 0.03 to 0.6 (theoretical value of 1) were determined, depending on the type of IL. The highest conductivity was achieved when ILs were confined within ionic domains with a sharp interface, owing to the creation of less tortuous ion conduction pathways. In contrast, a high degree of intermixing of ionic and nonionic domains at the interface, because of IL incorporation, revealed a reduction by 1 order of magnitude in the conductivity. This work presents fascinating experimental insights into confinement- and interface-driven modulation of ion transport properties for polymer electrolytes and presents the future prospects for designing desired nanostructures as efficient ion conductors.

We report a rational design of solid-state dry polymer electrolytes with high conductivity, high mechanical strength, and improved cation transference number. Thiol–ene click chemistry provided orthogonal control over the type and number of end groups in poly­(styrene-b-ethylene oxide) (PS-b-PEO) block copolymers. This approach permitted the synthesis of PEO chains with reduced crystallinity, reminiscent of PEO oligomers, thereby playing a key role in improving the room temperature conductivity. Intriguingly, the incorporation of diol or dicarboxylic acid end groups in PS-b-PEO produced a well-defined gyroid structure, leading to order of magnitude improvements in the storage modulus. Out of the various samples examined, the electrolytes bearing terminal diol displayed the highest ionic conductivity and a 2-fold increase in lithium transference number. The improvements in performance are attributed to the reduced interchain aggregation and the anion stabilization mediated by the terminal diol group. The fact that the dramatic changes in ion transport and mechanical properties of PS-b-PEO samples were brought about solely by the modification of single terminal group of the PEO unit confirmed end-group chemistry as a powerful tool for the design of efficient solid-state polymer electrolytes. This work should find applications in various emerging electrochemical technologies, namely those employed in energy storage and conversion.