Figure 2. Double Cantilever Beam tests of self-healing interfaces.

(a) Representative force/displacement curves of DCB tests (inset) carried out for 3 different interfaces at a rate of 1 mm/min (the interface thickness is much smaller than that of the substrates). For PBS and the reversible polymer, 1 mm thick glass plates have been used. The supramolecular UPy interfaces (5 μm thick) are highly adhesive and strong, resulting in the fracture of the thin (1 mm) glass substrates (measurements reported in this figure been performed with thicker-1 cm, substrates). The curve also shows a characteristic stick-slip behavior (multiple peaks) as it is commonly observed in some polymers. It could be related to inhomogneities in the coating or be an intrinsic characteristic of the polymer itself ³¹. The reversible adhesive interfaces (30 μm thick) exhibit very low degrees of adhesion when compared to PBS interfaces (20 μm thick). (b) Evolution of the degree of healing of the same sample (percentage of strength recovered) with time after closure. The reversible adhesive shows very poor recovery of the interfacial strength. The UPy polymer shows good initial healing, however, multiple healings are difficult and interfacial adhesion deteriorates after several cycles. In both cases less than 60% of the strength is recovered and it seems to saturate few minutes after closure. The shear thickening-PBS interface can instead recover full strength as the polymer flows and reforms the 20 μm interface without applying pressure.