Controlling the Functional Properties of Oligothiophene Crystalline Nano/Micro-Fibers via Tailoring of the Self-Assembling Molecular Precursors

F. Di Maria, M. Zangoli, M. Gazzano, E. Fabiano, D. Gentili, A. Zanelli, A. Fermi, G. Bergamini, D. Bonifazi, A. Perinot, M. Caironi, R. Mazzaro, V. Morandi, G. Gigli, A. Liscio, G. Barbarella
Adv. Funct. Mater., 2018, 28 (32), 1801946.
DOI: 10.1002/adfm.201801946


Oligothiophenes are π-conjugated semiconducting and fluorescent molecules whose self-assembly properties are widely investigated for application in organic electronics, op-toelectronics, biophotonics and sensing. We report here an approach to the preparation of crystal-line oligothiophene nano/micro-fibers based on the use of a ‘sulfur overrich’ quaterthiophene building block, -T4S4-, containing in its covalent network all the information needed to promote the directional, π-π stacking driven, self-assembly of Y-T4S4-Y oligomers into fibers with hier-archical supramolecular arrangement from nano- to microscale. We show that when Y varies from unsubstituted thiophene to thiophene substituted with electron withdrawing groups, a wide redistribution of the molecular electronic charge takes place without substantially affecting the aggregation modalities of the oligomer. In this way a structurally comparable series of fibers is obtained having progressively varying optical properties, redox potentials, photoconductivity and type of prevailing charge carriers (from p- to n-type). A thorough characterization of the fibers based on SEM, CD, CV, X-ray diffraction, UV-vis and PL spectroscopies, photoconductivity and KPFM measurements is reported. With the aid of DFT calculations, combined with powder X-ray diffraction data, a model accounting for the growth of the fibers from molecular to nano- and microscale is proposed.

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