Substrate steered crystallization of naphthyl end-capped oligothiophenes into nanofibers: the influence of methoxy-functionalizationElectronic supplementary information (ESI) available: Orientation and polarization angles of nanofibers, thickness dependence of NaT3 growth, correlation plots of NaT3 on phlogopite mica, details of the fluorescence spectra, and synthesis schemes for NaT3/MONaT3. See DOI: 10.1039/c3cp53881h

Naphthyl end-capped oligothiophenes are a class of materials well suited for high-performance organics based devices. The formation of nanofibers on muscovite mica from 2,5-bis(naphth-2-yl)thiophene (NaT), 5,5′-bis(naphth-2-yl)-2,2′-bithiophene (NaT2), and 5,5′′-bis(naphth-2-yl)-2,2′:5′,2′′-terthiophene (NaT3) as well as of the methoxy-functionalized variants MONaT, MONaT2, and MONaT3 is investigated via atomic force microscopy, X-ray diffraction, polarized fluorescence microscopy, and fluorescence spectroscopy. From polarized fluorescence microscopy spatially resolved molecular orientations are deduced revealing a profound anisotropy. Fibers from lying molecules grow along distinct substrate directions. Methoxy-functionalization substantially increases the crystallization into aligned fibers. In air Ostwald ripening is observed. The morphological variations of the aggregates result in specific optical signatures, disclosed by temperature dependent and spatially resolved fluorescence spectra. Fluorescence microscope images of NaT3 (left) and MONaT3 (right) demonstrating the influence of methoxy-functionalization on fiber growth.