Self-Healing, Reprocessable, and Degradable Bio-Based Epoxy Elastomer Bearing Aromatic Disulfide Bonds and Its Application in Strain Sensors

Abstract

A dicarboxylic acids functional aromatic disulfide (DTSA) and a dimer aliphatic acid (DAA) were used to crosslink epoxidized soybean oil (ESO) to obtain a bio-based epoxy elastomer with comprehensive properties of toughness and stretchability. This work addresses some urgent needs for epoxy networks, such as recyclability, degradability, and mechanical properties. Ratios of permanent and dynamic crosslinks were tuned to yield epoxy elastomers with various characteristics. The biobased epoxy elastomer in this work took advantages of dynamic aromatic disulfide bonds which can rapidly exchange even at room temperature without external stimuli. Therefore, the epoxy elastomer reported here presented almost quantitative self-healing efficiency and high recovery in terms of mechanical properties after being reprocessed for many times. Besides, incorporation of permanent chemical crosslinks with DAA caused low hysteresis, which made them suitable for fabricating sensitive and durable strain sensor against cyclic strain.

Functional Epoxy Elastomer Integrating Self-Healing Capability and Degradability for a Flexible Stretchable Strain Sensor

“…The mechanical and thermomechanical performances of the PEG-SS 8 -ESO y ( y = 0.1, 0.2, 0.3, and 0.4) elastomers were also studied (Figure S4b,c). Compared with relevant self-healing epoxy composites and bio-based materials, the PEG-SS x -ESO 0.2 ( x = 4, 6, 8, and 10) elastomers exhibited lower T g , higher tensile stress, and elongation at break (Figure h). ,,,− Meanwhile, the crosslinking densities ( ν c ) of the PEG-SS x -ESO 0.2 ( x = 4, 6, 8, and 10) elastomers were also calculated according to the storage modulus at the rubbery plateau ( T g + 40 K). The ν c of all of the samples were in a narrow range of 205.7–222.1 mol/m 3 (Table S4).…”

“…However, the elastomer was only degraded in a specific mixed organic solution of dichloromethane with excess trifluoroacetic acid, O -ethylhydroxylamine, and benzaldehyde. To date, it is still a great challenge to prepare self-healing and degradable elastomers with excellent mechanical performances for high-performance and environmentally friendly flexible strain sensors. , …”

“…Figure 3b presents the relationship between ln(τ) and 1000/ T and the E a was calculated to be 70.07 kJ/mol according to the slope of the linear fitting curve and similar to the reported self-healing elastomer with disulfide bonds. 38,45,48,49 The disulfide bond content also had a significant effect on the relaxation times of the epoxy elastomers. It was obvious to note that with the increase of the disulfide bond content, the relaxation time increased from 69 to 229, 348, and 1279 s (Figure 3c).…”

“…To date, it is still a great challenge to prepare self-healing and degradable elastomers with excellent mechanical performances for high-performance and environmentally friendly flexible strain sensors. 37,38 In this work, a series of functional epoxy elastomers with self-healing capability and degradability for flexible strain sensors were synthesized with carboxyl-terminated poly-(ethylene glycol), 2,2′-dithiodibenzoic acid, and 1,4-butanediol diglycidyl ether as monomers and bio-based epoxidized soybean oil as the crosslinker. Thanks to the synergistic healing effect of the hydrogen bonds and disulfide bonds, the elastomer exhibited good self-healing performance with a healing efficiency of 92.5% at 80 °C for 24 h. In addition, the generated β-hydroxyl ester bonds endowed the elastomer with degradability in alkaline solution.…”

From stretchable and healable to self-healing semiconducting polymers: design and their TFT devices

“…142,143 Hydrogen bonds, - interactions, metal-ligand bonds, ionic bonds, host-guest complexes, and hydrophobic interactions are the interaction found in non-covalent bonds, [144][145][146][147][148][149][150][151] while the Schiff base interactions, Diels-Alder interactions, and borate-ester and disulfide bonds are included in the common dynamic covalent bonds. [152][153][154][155][156] In addition to the bond interactions, the physical molecular diffusion also plays crucial part in determining the healing rate and characteristics of the damaged polymer surface. [157][158][159][160] The diffusion parameters include: the chemical characteristics, the chain length, polydispersity indices, and the mechanical properties of the polymer.…”