A Highly Stretchable, Self-Healing Elastomer with Rate Sensing Capability Based on a Dynamic Dual Network

Abstract

Flexible sensing materials have attracted tremendous attention in recent years because of their potential applications in the fields of health monitoring, artificial intelligence, and so on. However, the preparation of rate sensing materials with self-healing performance is always a huge challenge. Herein, we first report the design and synthesis of a highly stretchable, recyclable, self-healing polysiloxane elastomer with rate sensing capability. The elastomer is composed of a dynamic dual network with boron/oxygen dative bonds and hydrogen bonds, which overcomes the structural instability of conventional solid–liquid materials. It exhibits certain adhesion, satisfactory mechanical robustness, and superior elongation at break (up to 1171%). After heating treatment at 80 °C for 2–4 h, the mechanical properties of damaged materials can be almost completely restored. Because of the “solid–liquid” property of the elastomer, it has irreplaceable functions which can sense different rates by resistance change after blending with multiwalled carbon nanotubes, principally in the range of 10 mm/min–150 mm/min. Especially, this rate sensing elastomer can be personalized by 3D printing at room temperature. This rate sensing strategy coupled with the introduction of dynamic dual-network structure is expected to help design advanced wearable devices for human rhythmic movement.

Correlations Between Precursor Molecular Weight and Dynamic Mechanical Properties of Polyborosiloxane (PBS)

“…All PBS samples were easily dissolved in THF and chloroform which is additional evidence of the absence of the covalent 3D network. In a study by Qu, [3] where the same synthesis route was used molecular weight less than doubled due to a lower amount of BA closer to the stoichiometric ratio. In another work, [25] where PBS was synthesized using Piers-Rubinsztajn reaction, the molecular weight was increased by slightly more than two times and was dissolvable in common solvents.…”

“…This interaction is represented in two bands at 890 and 681 cm −1 . [3] These two frequencies are fingerprints of the B─O─H band and are present in pure BA (Figure 4). Intensities of these two peaks change in the same fashion as the Si─O─B band from the highest value for PBS 25, to almost invisible peaks starting from PBS 750 due to the absence of polymerization and crosslinking.…”

“…[1] The most common and utilized SSG is polyborosiloxane (PBS). PBS is a viscoelastic gel which is a result of B(OH) x (where x can be two, one, or zero depending on stoichiometry of the reaction) group modification of polydimethylsiloxane (PDMS) chains, either via condensation reaction DOI: 10.1002/mame.202100360 between hydroxy end groups of boric acid (BA) and PDMS, [2][3][4][5][6][7] borono termination reaction of scissored PDMS pieces [8][9][10] due to random chain scission of PDMS chains at a temperature higher than 150 °C with the presence of BA as a catalyst, [8,9] or simultaneous polymerization of PDMS with borono ends modification from dichlorodimethylsilane. [11,12] Incorporated B(OH) x groups possess sticker-like behavior due to their supramolecular interactions, such as Si─O: B dative bonding between borono end groups and oxygen in PDMS chains, hydrogen bonding between PDMS borono end groups, and topological entanglements.…”

“…[16] PBS is also found in other foam-based composites, [17,18] Kevlar-based composites, [19,20] and double network composites. [2][3][4] Despite the wide range of various PBS composites for impact protection, the potential of PBS itself has hardly been studied. This might be due to complications with the molding of PBS for real applications since it flows at low deformation rates.…”

Dynamic Polyphosphazene Networks with Modulating Shape Memory and Self‐Healing Capacity by Double Coordination Interactions

“…[ 15–17 ] However, there are few reports about recyclable and self‐healing polyphosphazene, while similar studies are popular in polysiloxane. [ 18–20 ]…”