Colour responsive smart polymers and biopolymers films through nanodispersion of organic chromophores and metal particles

Molecular optical brighteners incorporated into filmable polymers to a very low extent from 0.05 to 0.5 wt.% by melt-processing, provide materials which show a well-defined excimer emission by increasing dye concentration flanked by a characteristic change of the luminescent properties of the films. Then, the original colour of the film, provided by the radiative transitions of the isolated dye molecules, may be restored after polymer stretching that promotes the aggregates break-up and the alignment of the single chromophore molecules along the stretching direction thus providing an easy detectable colour change. The approach can be extended to polymer blends allowing to obtain a wide range of films with different structure and performances in colour changes determined by external stimuli. Also, nanostructured polymer films with unusual and anisotropic optical properties can be obtained through the dispersion of gold and silver nanoparticles. The metal nanoparticles can be produced directly inside the polymer matrix by a photo-reduction process. Both organic chromophores and metal particles nanostructured systems can be used to prepare "smart" coating materials with a broad type of structural characteristics and capable to detect and stores external stimuli of different origin and under different conditions.