Stretchable, robust and reprocessable poly(siloxane-urethanes) elastomers based on exchangeable aromatic disulfides

ACS Appl. Mater. Interfaces

et al. 2021

Self Cite

Strain sensors with high sensitivity, long-term durability, and stretchability are required for flexible and wearable electronic devices. This paper reports a bilayer strain sensor consisting of carboxyl-functionalized carbon nanotubes (CNTs) and ionically crosslinked polysiloxane substrates based on unsaturated acid–amine interactions. Vacuum filtration was adopted to prepare the CNT films (2.74–4.70 μm in thickness) onto the polysiloxane substrates to prepare stretchable conductive strain sensors. The strain sensor exhibited self-healing ability, self-adhesiveness, high sensitivity, linearity, low hysteresis, and long-term durability with a gauge factor of 33.99 at 55% strain. The sensitivity and linearity could be adjusted by the thickness of the CNT layer. A crack-related mechanism was proposed in which increasing the thickness of the CNT layer led to simultaneously enhanced sensitivity and linearity. Finally, we investigated the detection of human activities (bending/unbending of fingers or knees) and subtle motions (coughing and swallowing). The fabricated strain sensor succeeded in meeting various needs with satisfactory sensing performance.

Section: Experimental Sectionmentioning

confidence: 99%

Self-Healing, Self-Adhesive Strain Sensors Made with Carbon Nanotubes/Polysiloxanes Based on Unsaturated Carboxyl–Amine Ionic Interactions

Mai

ACS Appl. Mater. Interfaces

et al. 2021

Self Cite

“…It can be observed that the curves of the healed sample almost overlaid the pristine ones, verifying the good self-healing ability in terms of mechanical properties of the epoxy elastomer. These results are ascribed to the previously published works. − ,− Specifically, the dynamic aromatic disulfide bonds can exchange even at room temperature, which facilitates self-healing at low temperatures without extra stimuli. Meanwhile, the inherently high flexibility of aliphatic segments is also beneficial for self-healing.…”

Section: Resultsmentioning

confidence: 99%

“…Incorporation of dynamic covalent bonds to conventional networks offers a promising strategy to prepare CANs which possess the properties of both thermosets and thermoplastics at different temperatures. CANS can be efficiently rearranged due to the connection and disconnection of dynamic covalent bonds, such as transesterification, − and Schiff base, − boroxine, − disulfide, − and diselenide formation . The disulfide bond, as an attractive dynamic covalent bond, is sensitive and responsive to pH, light, and redox stimuli .…”

Section: Introductionmentioning

confidence: 99%

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

ACS Appl. Polym. Mater.

Mai

Lin

et al. 2021

Self Cite

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.

“…A gradient side-chain density can be obtained by exploiting the reactivity of GM as brushes. Aromatic disulfides (AFD) were subsequently blocked onto the backbone and used to synthesize self-healing and recycling bottlebrush polyurethane elastomer. − Three important structural parameters are focused here: the degree of polymerization of backbone (DP backbone ) and side chain (DP side chain ), and the molecular weight between neighboring side chains ( N sc ). GM brushes were chosen due to accurately controlled DP side chain of stearic tails.…”

Section: Introductionmentioning

confidence: 99%

Tough, Self-Healing, Recyclable Bottlebrush Polyurethane Elastomer with a Skin-like Strain-Adaptive-Strengthening Property

ACS Appl. Polym. Mater.

Lin

et al. 2022

Self Cite

Bottlebrush polymers consisting of linear polymer backbone and polymeric side-chains are of significant interest for an extensive variety of potential applications that include drug delivery, omniphobic surface, and amphiphilic emulsion surfactants. These polymers are challenging to prepare in large quantities for practical use. Therefore, it is necessary to provide a facile synthetic route for bottlebrush polymers with commercially available products. Here, we describe a simple approach to converting widely used linear poly(tetramethylene ether glycol) (PTMG) polyurethanes into a bottlebrush elastomer with extraordinary self-healing and recycling properties. Random and block distributed glyceryl monostearate (GM) brushes result in distinguishing mechanical and surface properties of the bottlebrush elastomer. The exchangeable character of aromatic disulfides facilitates the self-healing processes by temperature-, stress-, or solvent-induced arrangements, enabling a deformed sample to recover its original appearance and mechanical properties after applications of the self-healing and recycling process. The material manifested a self-healing recovering efficiency of 86% of tensile strength, above 90% of elongation at break, and a complete recovery of tensile strength after the reforming process. Other dynamic thermomechanical and surface properties, such as rheological analysis, DMA, DSC, and contact angles were investigated and compared with those of conventional PTMG polyurethanes. Furthermore, inspired by biological tissues and real human skin, a stain-adaptive-strengthening effect in tensile measurements was observed with highly correlated polynomial fittings with R 2 = 0.9996. This simple and easy approach to preparing bottlebrush polyurethane elastomer with skin-like, self-healing, and recycling properties offers unique opportunities in the field of advanced materials, such as surgical skin dressing, intelligent sensors, human−machine interaction, and soft robotics.