Substrate‐Independent, Reversible, and Easy‐Release Ionogel Adhesives with High Bonding Strength

Abstract

structures to enhance the van der Waals interactions with the substrate. [5-7] Reversible and stimuli-responsive adhesives can also be fabricated based on stimuliresponsive polymers or polymer systems involving reversible and dynamic molecular interactions, such as the introduction of temperature or light isomerization groups, [8-10] dynamic covalent bonds [11,12] (e.g., Diels-Alder reaction, disulfide bonds) and reversible noncovalent interactions [13-20] (e.g., hydrogen bonds, metal-ligand and host-gust interactions). However, these adhesives were mostly reported to exhibit high-performance bonding with high-surface-energy substrates, such as glass and metal. The adhesion of inert low-surface-energy substrates, typically exampled by polytetrafluoretyhylene (PTFE), has been a long-standing challenge, because such substrates resist wetting and possess limited functional groups to form interfacial interactions with the adhesives. [21] Therefore, it is still highly desirable to develop substrate-independent, reversible and easyrelease temporal adhesives with high bonding strength. For the temporal adhesives that bond substrates based on their intrinsic viscoelastic properties, the bonding performance depends on both the adhesive and cohesive strength. [22-28] The adhesive strength is determined by the wetting ability of the adhesive and the interfacial interactions between the adhesive and substrates, whereas the cohesive strength depends on the mechanical rigidity of the adhesive. [26-28] Therefore, the adhesive with higher cohesive strength should be more solid-like with lower deformability, which, however, would prevent the wetting of the substrates by the adhesive and in turn may result in lower bonding performance. Conversely, the adhesives with higher adhesive strength should be more fluid-like with higher deformability, which would result in lower cohesive strength and thus may lower the bonding performance as well. Therefore, it is a big challenge to optimize the viscoelastic properties of a temporal adhesive to balance the adhesive and cohesive strength to maximize the bonding performance. Herein, taking advantages of the good wetting ability and nonvolatility of ionic liquids (IL), [29-31] ionogel adhesives are prepared by blending an imidazolium-based IL with a copolymer bearing charged quaternary amine groups. Homogeneous and stable ionogels can be obtained due to the electrostatic interactions between the charged moieties of the IL and the copolymer. The IL can promote the continuous contact between the

Water‐Resistant Ionogel Electrode with Tailorable Mechanical Properties for Aquatic Ambulatory Physiological Signal Monitoring

“…[44,45] During the underwater adhesion of ionogels, the hydration layer on the substrate surface can be destroyed due to the hydrophobicity of the ionogels. Then, various interactions, such as ion-dipolar, [31,46,47] dipolar-dipolar, [48][49][50] metal complexation, [51] electrostatic, [44,52] cation-π interactions, [44] and van der Waals interactions, [53] can be formed between the ionogels and different substrates (Figure S8, Supporting Information). Therefore, underwater strong adhesion can be formed.…”

Highly Stretchable, Adhesive Ionic Liquid-Containing Nanocomposite Hydrogel for Self-Powered Multifunctional Strain Sensors with Temperature Tolerance

“…The results are displayed in Figure a, and the adhesive strength of nanocomposite ionogels to glass, plastic, aluminum, and cooper reached 13.21 ± 0.68 kPa, 24.31 ± 2.52 kPa, 23.20 ± 2.29 kPa, and 2.24 ± 1.52 kPa, respectively. The P­(AAm- co -HEA)-Laponite XLG ionogel exhibited the highest adhesion strength to the copper sheet, probably due to the coordination interactions and hydrogen bonding synergistic effects between the ionogel and copper. , The corresponding test curves of the adhesive strength to different substrates are depicted in Figure b. In addition, the repeated and durable adhesion performance of nanocomposite ionogels was investigated by 10-time consecutive adhesion/peeling-off tests (Figure c).…”

“…The P(AAm-co-HEA)-Laponite XLG ionogel exhibited the highest adhesion strength to the copper sheet, probably due to the coordination interactions and hydrogen bonding synergistic effects between the ionogel and copper. 58,59 The corresponding test curves of the adhesive strength to different substrates are depicted in Figure 5b. In addition, the repeated and durable adhesion performance of nanocomposite ionogels was investigated by 10-time consecutive adhesion/peeling-off tests (Figure 5c).…”

Robust Antiwater and Anti-oil-fouling Double-Sided Tape Enabled by SiO2 Reinforcement and a Liquefied Surface

“…To overcome the loss of adhesion against wet or oil-fouling surfaces, the attachment systems of organisms capable of forming adhesion in a natural environment have been widely studied. − Inspired by the fascinating adhesion capacity of living organisms, much effort has been devoted to the elaborate structure design and composition selection of adhesives, for example, the biostructures, − mussel-inspired and catechol-based polymeric materials, − and ionic hydrogels. ,− These strategies significantly enhance the underwater adhesion of adhesives. However, unlike numerous studies for antiwater adhesives, anti-oil-fouling ones are rarely reported.…”

“…The tape should be soft with high interfacial adhesive energy to realize fast bonding, which usually sacrifices the cohesive energy and vice versa. , Although no scaling theory guides us to overcome such a trade off, it is required to obey Cannikin’s law, that is, not sacrificing one performance distinctively, the other performance is improved significantly. Recently, there are six approaches to relieve this dilemma: (1) combining dynamic bonds with bioinspired surface drainage architecture or catechol moiety, ,− (2) synergetic effect between a hydrophobic backbone and hydrophilic adhesive side branches, ,, (3) modification of poly­(ionic liquid)­s (PILs), ,, (4) sequence-controlled poly­(cation-π)­s, ,,, (5) introduction of dual cross-linking networks, , and (6) composite with nanofillers. − Nevertheless, abovementioned adhesives with a high adhesion strength usually are glue-type adhesives, which need UV, heat, an extra cross-linking agent, or long-time to cure, while hydrogel-type adhesives still cannot achieve high bonding strength limited by their weak cohesive strength.…”