Property tuning and supramolecular organization of oligo- and polythiophenes for applications in biology and organic electronics

My research activity was focused on the synthesis and characterization of novel thiophene-based oligomers and polymers for the preparation via self-assembly of nanoparticles (0D) and fibers (1D) aimed to application in organic electronics and biophotonics. The first chapter shows an overview of the most recent developments in synthesis and application of oligo- and polythiophenes as organic materials, highlighting the state of the art in synthetic procedures, performances in devices and application in biology as fluorescent probes. The second chapter reports the synthesis of novel classes of selectively sulphur-oxidized oligo- and polythiophenes. Oligomers and polymers containing thiophene-S,S-dioxide and thiophene-S-oxide units in the desired number and position are described. Examples of their application in devices and supramolecular organization inside live cells are given. The third chapter is dedicated to the preparation and characterization of polythiophene based nanoparticles for biophotonics. It is demonstrated that live cells easily uptake poly(3-hexylthiophene) nanoparticles (P3HT-NPs) without toxic effects while preserving their physiological functions. In addition, it is reported that P3HT-NPs can act as “photosensitizers” after internalization in live animals, Hydra vulgaris, modifying their behaviour and genic expression upon white light irradiation. Finally, the preparation of amino-reactive NPs, obtained from a properly functionalized polythiophene, is reported. The ability of the nanoparticles to remain docked on cell membrane and to act as phototransducers under illumination is demonstrated. The fourth chapter reports the synthesis and the supramolecular organization in crystalline, fluorescent and electro-active fibers of oligothiophenes possessing the same core properly functionalized. Further functionalization of the quaterthiophene with different electron withdrawing aromatic terminal units causes the variation of the electronic distribution without altering the growth modalities. In this way a wide tuning of the optical and redox properties of the fibers is obtained. Studies on the effects of the terminal substituents on charge transport properties are currently under way.