Polymers do not only, as during the last century, ensure elementary functions such as structural, conductive, optical ones etc, but moreover, with the dawn of the new millennium, they must be intelligent and must adapt to their environment to ensure an optimization of their behaviour or that of the system to which they are built-in.
Among the best-known examples and the simplest ones, let us quote:
* Photochromic lenses darkening with the sunlight and fading indoors.
* Thermo-shrinkable sheaths shrinking when heated.
These materials adapting their optical properties or shape to an environmental stimulus are called smart or intelligent polymers. Figure 1 displays a schematic example for photochromic polycarbonate lense.
Photochromic principle.The polymer receives from its environment a stimulus that involves the adaptation of one of its properties according to the intensity of the stimulus. For example, in the case of the thermometric bands for external control of the frontal human temperature this one involves a change of precise colour for each level of fever. The eye, alone, interprets these colour changes without contribution of other devices.