Mixed Conductive, Injectable, and Fluorescent Supramolecular Eutectogel Composites.

Eutectogels are an emerging family of soft ionic materials alternative to ionic liquid gels and organogels, offering fresh perspectives for designing functional dynamic platforms in water-free environments. Herein, the first example of mixed ionic and electronic conducting supramolecular eutectogel composites is reported. A fluorescent glutamic acid-derived low-molecular-weight gelator (LMWG) was found to self-assemble into nanofibrillar networks in deep eutectic solvents (DES)/poly(3,4-ethylenedioxythiophene) (PEDOT): chondroitin sulfate dispersions. These dynamic materials displayed excellent injectability and self-healing properties, high ionic conductivity (up to 10-2  S cm-1 ), good biocompatibility, and fluorescence imaging ability. This set of features turns the mixed conducting supramolecular eutectogels into promising adaptive materials for bioimaging and electrostimulation applications.

Natural Deep Eutectic Solvents Based on Choline Chloride and Phenolic Compounds as Efficient Bioadhesives and Corrosion Protectors.

Natural deep eutectics solvents (NADES), owing to their high solvation capacity and nontoxicity, are actively being sought for many technological applications. Herein, we report a series of novel NADES based on choline chloride and plant-derived polyphenols. Most of the obtained phenolic NADES have a wide liquid range and high thermal stability above 150 °C. Among them, small-sized polyphenols, like pyrogallol, vanillyl alcohol, or gentisic acid, lead to low-viscosity liquids with ionic conductivities in the order of 10-3 S cm-1 at room temperature. Interestingly, polyphenols possess valuable properties as therapeutic agents, antioxidants, adhesives, or redox-active compounds, among others. Thus, we evaluated the potential of these novel NADES for two applications: bioadhesives and corrosion protection. The mixture of choline chloride-vanillyl alcohol (2:3 mol ratio) and gelatin resulted in a highly adhesive viscoelastic liquid (adhesive stress ≈ 135 kPa), affording shear thinning behavior. Furthermore, choline chloride-tannic acid (20:1) showed an extraordinary ability to coordinate iron ions, reaching excellent corrosion inhibitive efficiencies in mild steel protection.

Gelatin and Tannic Acid Based Iongels for Muscle Activity Recording and Stimulation Electrodes.

Iongels are soft ionic conducting materials, usually composed of polymer networks swollen with ionic liquids (ILs), which are being investigated for applications ranging from energy to bioelectronics. The employment of iongels in bioelectronic devices such as bioelectrodes or body sensors has been limited by the lack of biocompatibility of the ILs and/or polymer matrices. In this work, we present iongels prepared from solely biocompatible materials: (i) a biobased polymer network containing tannic acid as a cross-linker in a gelatin matrix and (ii) three different biocompatible cholinium carboxylate ionic liquids. The resulting iongels are flexible and elastic with Young's modulus between 11.3 and 28.9 kPa. The morphology of the iongels is based on a dual polymer network system formed by both chemical bonding due to the reaction of the gelatin's amines with the polyphenol units and physical interactions between the tannic acid and the gelatin. These biocompatible iongels presented high ionic conductivity values, from 0.003 and up to 0.015 S·cm-1 at room temperature. Furthermore, they showed excellent performance as a conducting gel in electrodes for electromyography and electrocardiogram recording as well as muscle stimulation.

Single-Ion Lithium Conducting Polymers with High Ionic Conductivity Based on Borate Pendant Groups.

A family of single-ion lithium conducting polymer electrolytes based on highly delocalized borate groups is reported. The effect of the nature of the substituents on the boron atom on the ionic conductivity of the resultant methacrylic polymers was analyzed. To the best of our knowledge the lithium borate polymers endowed with flexible and electron-withdrawing substituents presents the highest ionic conductivity reported for a lithium single-ion conducting homopolymer (1.65×10-4  S cm-1 at 60 °C). This together with its high lithium transference number t Li + =0.93 and electrochemical stability window of 4.2 V vs Li0 /Li+ show promise for application in lithium batteries. To illustrate this, a lithium borate monomer was integrated into a single-ion gel polymer electrolyte which showed good performance on lithium symmetrical cells (<0.85 V at ±0.2 mA cm-2 for 175 h).

Partially Reversible H2S Adsorption by MFM-300(Sc): Formation of Polysulfides.

The metal-organic framework (MOF)-type MFM-300(Sc) exhibits a combined physisorption and chemisorption capture of H2S, leading to a high uptake (16.55 mmol g-1) associated with high structural stability. The irreversible chemisorbed sulfur species were identified as low-order polysulfide (n = 2) species. The isostructural MFM-300(In) was demonstrated to promote the formation of different polysulfide species, paving the way toward a new methodology to incorporate polysulfides within MOFs for the generation of novel MOF-lithium/sulfur batteries.

Electrochemical Characterization of Single Lithium-Ion Conducting Polymer Electrolytes Based on sp3 Boron and Poly(ethylene glycol) Bridges.

A novel series of single lithium-ion conducting polymer electrolytes (SLICPE) based on sp3 boron and poly(ethylene glycol) (PEG) bridges is presented, in the context of the development of a new generation of batteries, with the aim to overcome the problems related to concentration overpotential and low ion transport numbers in conventional solid polymer electrolytes (SPE). The phase separation generated by the physical mixture of SPE with plasticizers such as poly(ethylene oxide) is still a serious problem. In this work, the use of PEG with different chain lengths, for the polycondensation reaction with LiB(OCH3)4, to synthesize SLICPE allows preventing phase separation while tuning the predominant conduction mechanism, and thus the electrical properties, especially the lithium-ion transference number. The ionic transport is promoted by chain mobility as the chain length is increased. SLICPE with the best ionic conductivity values (4.95 ± 0.05) × 10-6 S cm-1 was the one synthesized from poly(ethylene glycol) with an average MN of 400 (BEG8), having an O/Li+ ratio of 20. The lithium transference number ( tLi+) and electrochemical stability window of SLICPE membranes at 25 °C decreased as the PEG bridge length between sp3 boron atoms increased from 0.97 to 0.88 and 5.4 to 4.2 V vs Li0/Li+, respectively, for SLICPE synthesized from PEG with an average MN of 50-400 (BEG1 to BEG8).