by judiciously adjusting the structure of ILs. ILs have been intensively studied as a "green" alternative to organic solvents for synthesis, catalysis, extraction, and separation. [2] They are also safe and versatile electrolytes for electrochemistry and energy-related applications. [3] However, their viscosities are generally two or three orders of magnitude higher than those of conventional organic solvents (molecular liquids), which inevitably lead to handling difficulties (e.g., infiltration, decantation, and dissolution), low reaction rates, competitive unimolecular side reactions, sluggish ionic transport, and significantly reduced ionic conductivity. [4] For the potential application of ILs, such high viscosities have to be deliberately avoided by choosing alternative anions such as bis (trifluoromethanesulfonimide) (TFSI − ) and dicyanamide anions with high charge delocalization [4b,5] or introducing ether groups that pack less efficiently and provide more available free volume to enable low viscosity. [6] Nevertheless, the disadvantageous high viscosities of ILs can become advantageous for special applications that require viscous materials, such as adhesion, sealing, and gelation. [7] Particularly, adhesion is the attraction between two different condensed phases when they are in contact to construct a robust joint. Adhesion involves not only the molecular interactions at the interface of two individual surfaces but also the energy within the deformed material when pulling them apart. Adhesives have been acknowledged as indispensable chemicals in daily life and in many industries ranging from packaging, labeling, housing construction, and automobile manufacturing to soft robots, wearable devices, and aerospace. [7a,b,8] Along with conventional resins and gum-based adhesives, many musselinspired and catechol-based polymeric materials had been developed as modern adhesives in the past. [9] Nevertheless, they possess inherent drawbacks such as irreversible oxidizing crosslinking, tedious synthesis, and poor cycling performance. [10] We recently reported a series of noncatechol adhesive materials produced by water-triggered supramolecular polymerization of crown ether-containing monomers, but the synthesis of such specific monomers involves complicated functionalization, which is difficult to scale up. [11] The presence of water in these supramolecular adhesives also becomes an obvious disadvantage as they cannot bear ultra-high vacuum adhesion.Adhesive materials have wide applications in diverse fields, but the development of a novel and multipurpose adhesive is a great challenge. This study demonstrates that conventional poly(ionic liquid)s (PILs) can be designed as highly efficient adhesives by simply introducing alkoxy moieties into the cationic backbone of PILs containing bis(trifluoromethanesulfonimide) (TFSI − ) anions. The incorporated flexible alkoxy chain not only reduces the glass transition temperature of PILs but also endows these materials with strong hydrogen bonding interactions, w...
