Development of a liquid crystalline pressure-sensitive adhesive

While hydrogen bonds are often used for the construction of supramolecular structures, the hygroscopic nature often decreases the adhesive strength. We have previously developed a light-melt adhesive with strong non-hydrogen-bonding cohesive force due to a two-fold π-stacking structure of V-shaped flapping molecules (FLAP). Here we have developed a new FLAP molecule, dppz-FLAP, bearing an electron-deficient dipyridophenazine (dppz) wings that enhances the cohesive force of the supramolecular materials by constructing tighter two-fold columnar π-stacking structure. This material shows viscoelasticity and liquid-crystalline properties by introducing peripheral long alkyl chains. Actually, dppz-FLAP demonstrates high shear strength over 1 MPa as a supramolecular adhesive. Since the dppz-FLAP adhesive only needs to be pressed at room temperature for the adhesion process, it could be categorized into a pressure sensitive adhesive (PSA). Interestingly, the dppz-FLAP film pasted on a PET tape showed virtually no peeling stress. Therefore, dppz-FLAP is the first liquid-crystalline pressure sensitive adhesive (PSA) that shows high shear strength with easy peelability.