Zero volume unbonds (ZVU), or kissing bonds, cannot be detected by the conventional nan-destructive testing (NDE) techniques. These unbonds can cause premature failure in adhesive joints. Self-validating adhesives are being developed which detect and remove zero volume unbonds. It is hoped that this can be achieved by the addition of a secondary component to the primary adhesive. This material will be able to migrate through the matrix and 'fill' the ZVU and then cure or solidify over time, repairing the joint in situ. In order to determine the structure of the 'smart' adhesive, dynamic mechanical thermal analysis and differential scanning calorimetry have been employed. These have indicated the presence of multiple phases in certain formulations and the lack of them in others, as well as physical ageing of the amorphous polymer.