Ultrauniform Embedded Liquid Metal in Sulfur Polymers for Recyclable, Conductive, and Self‐Healable Materials

Abstract

Liquid metals (LMs) are receiving growing interest in modern technologies for their various advantages. This work reports using elemental sulfur to achieve nanodispersed liquid metals in bulk polymers for multifunctional LM-based materials. Ring-opening polymerization and inverse vulcanization of elemental sulfur provide many polysulfide loops and thiol groups as effective binding ligands that enable extraordinarily uniform dispersion of liquid metals (≈1 µm) in bulk matrix and improve the mechanical performance of the materials. Interestingly, the liquid-metal-embedded sulfur polymer (LMESP) materials exhibit excellent thermal-/solventprocessability and recyclability. The uniform dispersion leads to phenomenal electrical conductivity of the LMESP at a low volume percentage of LM (30 vol%), overcoming the issue of nonconductivity typically seen in insulated LM-polymer blends. Additionally, the LMESP shows resistive sensitivity toward external pressure. Furthermore, the LMESP materials exhibit an excellent self-healing ability under mild conditions via the dynamic bonds between polysulfide loops/thiol groups and liquid metals. This work clearly offers a new platform to design liquid metals and can push them for broad applications.

Transparent, Highly Stretchable, Rehealable, Sensing, and Fully Recyclable Ionic Conductors Fabricated by One‐Step Polymerization Based on a Small Biological Molecule

“…Moreover, the appearance of new peak at 673 cm −1 related to C‐S bonds demonstrated the realization of addition polymerization between AA and terminal diradicals of poly (LA) . Based on the Fourier transform infrared spectroscopy (FT‐IR) spectrum of the resultant polymer composite (Figure S5, Supporting Information), the observed changes of characteristic peaks (the reduced peak at 1714 cm −1 , increased peak at 3326 cm −1 , shifted peak at 622 cm −1 , and new peak at 1624 cm −1 ) could indicate the formation of hydrogen bonds, C‐S bonds, and Fe 3+ ‐carboxylated coordinative bonds in the polymer networks . Moreover, new shoulder‐like absorption peaks in the range of 342–348 nm were detected in UV–vis absorption spectrums (Figure S6, Supporting Information), further revealing the formation of coordination bonds …”

Liquid Metal–Based Soft Microfluidics

“…f) Tensile curves of the original sample and self‐healed sample after damaging. Reproduced with permission . Copyright 2019, John Wiley and Sons.…”

“…In the most recent studies, the self-healing of LM-based devices not only include the recovery of the electronic properties after damage, but also contains the recovery of the mechanical toughness and restretchability which is mainly depend on the encapsulating polymer materials. [112,118,119] As introduced in the section of 2D flexible electronics (Section 5.3), the LM-encapsulated sulfur polymer shows excellent self-healing properties in both the mechanical and electrical performance under mild conditions. [112] As shown in Figure 19f, the tensile curves of the self-healed sample after damaging matches well with the original sample.…”

“…[112,118,119] As introduced in the section of 2D flexible electronics (Section 5.3), the LM-encapsulated sulfur polymer shows excellent self-healing properties in both the mechanical and electrical performance under mild conditions. [112] As shown in Figure 19f, the tensile curves of the self-healed sample after damaging matches well with the original sample. The excellent self-healing performance in mechanical property is attributed to the sulfide bonds and chain entanglement, and the dynamic interaction between the thiol ligands and the liquid metal (Figure 19e).…”

Sequential crosslinking for mechanical property development in high sulfur content composites

“…[32][33][34][35] Polymeric sulfur domains can reform following their rearrangement by metathesis when the material is cooled back to room temperature, provided that the supporting network is intact , allowing materials to be reshaped or thermally healed. [6,22,26,[36][37][38][39][40] Two types of S S bonds are typically present in these materials: those in polymeric/oligomeric catenates that undergo metathesis at temperatures as low as 90 C and those in cyclic S 8 allotropes that generally require heating to above 159 C to undergo metathesis. In the absence of other species, the polymeric sulfur radicals are stable up until around 250 C, when a color change from red to black is noted.…”