The Unique Optical Behaviour of Biorelated Materials with Organic Chromophores

Molecularly designedmaterials based onmacromolecules and organic dyes offer unique opportunities in connectionwith the possibility of preparing optically responsive ‘smart’ materials. Indeed macromolecules are able to transmit and amplify small signals reaching sites at interacting distance through the involvement of the whole chain. The corresponding materials can then acquire stimuli-responsive properties in relation to specific features connected to primary structure and conformation. As a first approach to benefit from the above features for preparing eco-compatible smartmaterials, bio-related polypeptides, polysaccharides and polyesters can be used as the macromolecular partner in combination with a selected dye following different interaction methodologies. Two distinct routes were used to prepare optically responsive products from the above bio-related polymers, respectively based either on the covalent bonding to the original macromolecules of photochromic molecular species, such as azobenzene and spiropyran, or on the morphology-modulated dispersion of highly conjugated dyes in the polymer bulk. Examples related to the two different routes have been investigated in our laboratory and are presented and discussed alsowith reference to selected recent cases from the literature.