**3. Future outlook**

Thermal reversibility allows adding another tool for the design of smart composites. Properties such as self-healing and shape memory, besides the "classical effects" on thermal and mechanical ones, are easily added to the composite behavior. The sensitivity to multiple external stimuli such as electricity, irradiation, and heat [11, 18, 53, 54], represents a focal point for the design of smart materials. An added value in this case is the possibility (via irradiation) of remote-induced self-healing as well as of ultrafast kinetics [55]. In this context, it is conceivable that many research efforts will be spent in achieving a systematic control over this multifunctionality and responsiveness. In turn, this will require even more precise control over the kind of functional groups present and the chemical structure in more general terms. Further studies are then envisioned in the general field of structure-property relationships, for example, by a systematic investigation on the influence of spacers [56] on the DA decrosslinking. Other factors influencing the structure of the composite and thus its properties, such as the nature of the filler and the backbone, continue to represent points of attention. The possibility to extend the concept to inorganic polymers [57], the use of fullerene derivatives [58] as well the general trend toward the use of green fillers [59] have been recently reported, but deserve further study in order to explore all possible application fields. Finally, the combination of the properties highlighted above and their synergy with additional ones, such as color change upon thermally reversible behavior [60], constitute attractive characteristics of these materials.
