(14) Functional Polymeric Adhesives with Reversible and Movable Cross-links

Recently, various approaches have been tried to suppress negative environmental impact to realize sustainable resource-circulating society. Self-healable and tough adhesives are good approach toward the sustainable society. Previously, we have achieved tough and self-healing materials consisting of hydrophobic interaction as molecular adhesive functions of cyclodextrin. The obtained materials are self-healable and tough because of reversible complexation （supramolecular adhesive） of the cyclodextrin and guest molecules in response to external stimuli. The molecular adhesive enables both micro- and macroscopic self-healing properties which restores degraded function and appearance. Moreover, the molecular adhesive works on the glass and metal substrates not only in the materials. The adhesive function at the interfaces binds the two similar or dissimilar substrates such as glass-hydrogels and metal-metal. Moreover, additional covalent bond between the substrates improves the adhesion. Stimulus-responsive molecular adhesive controls the on-off adhesive properties. As a next-generation adhesive, we suggest polymeric material designs based on movable crosslinks. The movable cross-links allow mixing conventionally immiscible materials, resulting in novel functions such as toughness. We expect the diverse principles for the adhesives contribute to realizing the sustainable resource-circulating society.