Structure–Property Relationships for Polyether-Based Electrolytes in the High-Dielectric-Constant Regime

Multi-responsive Pickering emulsions stabilized by amphiphilic cellulose nanocrystals for building smart release systems of hydrophobic drugs

In this study, cellulose nanocrystals (CNC) were first extracted from peanut shells. Then, the monomers DMAEMA and MAA were grafted on the surface of CNC using reversible addition-fragmentation chain transfer (RAFT) polymerization to prepare multi-stimuli responsive nanoparticles (CNC/PDM), and they were used to stabilize Pickering emulsions. The effects of such factors as pH, nanoparticle concentration, water-to-oil ratio, and oil polarity on the stability of Pickering emulsions were investigated in detail. Pickering emulsions showed good smart response properties in pH, temperature and CO2 environmental stimuli. At the same time, the emulsifier showed excellent stability in various real oil phases, which had a wide range of practical applications. In addition, curcumin was encapsulated in the oil phase of the emulsions and the encapsulation efficiency (EE) was determined to be higher than 80 %. Simulated in vitro digestion experiments revealed that both the release of free fatty acids and the bioaccessibility of curcumin in curcumin-loaded emulsions were dramatically improved (bioaccessibility increased by about 4.3 times). Consequently, the present study provided an effective strategy for the preparation of multi-responsive Pickering emulsions, which offered new perspectives for improving the bioavailability of fat-soluble drugs.

Influence of Water Sorption on Ionic Conductivity in Polyether Electrolytes at Low Hydration

Ion-containing polymers are subject to a wide range of hydration conditions across electrochemical and water treatment applications. Significant work on dry polymer electrolytes for batteries and highly swollen membranes for water purification has informed our understanding of ion transport under extreme conditions. However, knowledge of intermediate conditions (i.e., low hydration) is essential to emerging applications (e.g., electrolyzers, fuel cells, and lithium extraction). Ion transport under low levels of hydration is distinct from the extreme conditions typically investigated, and the relevant physics cannot be extrapolated from existing knowledge, stifling materials design. In this study, we conducted ion transport measurements in LiTFSI-doped polyethers that were systematically hydrated from dry conditions. A semiautomated apparatus that performs parallel measurements of water uptake and ionic conductivity in thin-film polymers under controlled humidity was developed. For the materials and swelling range considered in this study (i.e., <0.07 g water/g dry polymer electrolyte), ionic conductivity depends nonlinearly on water uptake, with the initial sorbed water weakly affecting conductivity. With additional increases in swelling, more significant increases in conductivity were observed. Remarkably, changes in conductivity induced by water sorption were correlated with the number of water molecules per lithium ion, with the normalized molar conductivity of different samples effectively collapsing onto one another until this unit of hydration exceeded the solvation number of lithium ions under aqueous conditions. These results provide important knowledge regarding the effects of trace water contamination on conductivity measurements in polymer electrolytes and demonstrate that the lithium-ion solvation number marks a key transition point regarding the influence of water on ion transport in ion-containing polymers.

Decoupling Ion Transport and Matrix Dynamics to Make High Performance Solid Polymer Electrolytes

Transport of ions through solid polymeric electrolytes (SPEs) involves a complicated interplay of ion solvation, ion-ion interactions, ion-polymer interactions, and free volume. Nonetheless, prevailing viewpoints on the subject promote a significantly simplified picture, likening ion transport in a polymer to that in an unstructured fluid at low solute concentrations. Although this idealized liquid transport model has been successful in guiding the design of homogeneous electrolytes, structured electrolytes provide a promising alternate route to achieve high ionic conductivity and selectivity. In this perspective, we begin by describing the physical origins of the idealized liquid transport mechanism and then proceed to examine known cases of decoupling between the matrix dynamics and ionic transport in SPEs. Specifically we discuss conditions for "decoupled" mobility that include a highly polar electrolyte environment, a percolated path of free volume elements (either through structured or unstructured channels), high ion concentrations, and labile ion-electrolyte interactions. Finally, we proceed to reflect on the potential of these mechanisms to promote multivalent ion conductivity and the need for research into the interfacial properties of solid polymer electrolytes as well as their performance at elevated potentials.