Mussel‐Inspired, Underwater Self‐Healing Ionoelastomers Based on α‐Lipoic Acid for Iontronics

Abstract

Weak adhesion and lack of underwater self‐healability hinder advancing soft iontronics particularly in wet environments like sweaty skin and biological fluids. Mussel‐inspired, liquid‐free ionoelastomers are reported based on seminal thermal ring‐opening polymerization of a biomass molecule of α‐lipoic acid (LA), followed by sequentially incorporating dopamine methacrylamide as a chain extender, N,N′‐bis(acryloyl) cystamine, and lithium bis(trifluoromethanesulphonyl) imide (LiTFSI). The ionoelastomers exhibit universal adhesion to 12 substrates in both dry and wet states, superfast self‐healing underwater, sensing capability for monitoring human motion, and flame retardancy. The underwater self‐repairabilitiy prolongs over three months without deterioration, and sustains even when mechanical properties greatly increase. The unprecedented underwater self‐mendability benefits synergistically from the maximized availability of dynamic disulfide bonds and diverse reversible noncovalent interactions endowed by carboxylic groups, catechols, and LiTFSI, along with the prevented depolymerization by LiTFSI and tunability in mechanical strength. The ionic conductivity reaches 1.4 × 10−6–2.7 × 10−5 S m−1 because of partial dissociation of LiTFSI. The design rationale offers a new route for creating a wide range of LA‐ and sulfur‐derived supramolecular (bio)polymers with superior adhesion, healability, and other functionalities, and thus has technological implications for coatings, adhesives, binders and sealants, biomedical engineering and drug delivery, wearable and flexible electronics, and human–machine interfaces.

Study on fabricating transparent, stretchable, and self-healing ionic conductive elastomers from biomass molecules through solvent-free synthesis

“…Compared with recently reported self-healing hydrogels, ionic gels, or all-solid ionic conductors (Table S3†), 31–33,56,60,61,70,71 our THICE had comprehensive optical, mechanical, conductive, and stable properties. More importantly, our THICE was a biobased, solvent-free, self-healing, and recyclable elastomer, which is in accordance with the sustainable development of green chemistry.…”

“…S10†). This may be attributed to the reduction in the free energy of the copolymer by hydrogen bonding, increasing the stability of THICE and inhibiting the dynamic depolymerization of disulfide bonds 59–61 .…”

“…The synthesized THICEs had decent ionic conductivities compared to those reported for all-solid conductors, 27,29,32,33 which were approximately one or two orders of magnitude higher than those previously reported for TA all-solid ionic conductors. 60,61…”

“…This phenomenon was attributed to the alkene double bonds of HA stabilizing the TA/HA copolymer through inverse vulcanization. 34,49 The coordination bonds 34,35 and lithium bonds, 60,61 which were used to stabilize polyTA, have been reported. In order to further investigate the stabilizing effect of HA on TA, we prepared TA-HA copolymers without lithium salts or Al(III).…”

“…Although researchers have exploited a few successful systems to prepare high-performance elastomers or adhesives from TA, it remains very challenging to realize solid-state ionic conductors with high conductivities based on TA. 60,61 Due to strong complexation of the carboxyl groups, the conductivities of solid-state ICEs derived from TA are lower than 10 −4 S m −1 , which limits their application in the eld of so electronics. The use of solutions, ionic liquids, and deep eutectic solvents could signicantly improve the conductivity of polyTA; nevertheless, this would sacrice the rare advantage of using TA to prepare solid-state ICEs by reducing their thermal and electrochemical stabilities.…”