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Substrate‐Induced Phase of a Benzothiophene Derivative Detected by Mid‐Infrared and Lattice Phonon Raman Spectroscopy
Author(s) -
Schrode Benedikt,
Jones Andrew O. F.,
Resel Roland,
Bedoya Natalia,
Schennach Robert,
Geerts Yves Henri,
Ruzié Christian,
Sferrazza Michele,
Brillante Aldo,
Salzillo Tommaso,
Venuti Elisabetta
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201701378
Subject(s) - raman spectroscopy , benzothiophene , analytical chemistry (journal) , thin film , annealing (glass) , infrared spectroscopy , metastability , spectroscopy , materials science , phonon , crystal structure , crystallography , chemistry , organic chemistry , nanotechnology , optics , condensed matter physics , quantum mechanics , composite material , thiophene , physics
The presence of a substrate‐induced polymorph of 2,7‐dioctyloxy[1]benzothieno[3,2‐ b ]benzothiophene is probed in microscopic crystals and in thin films. Two experimental techniques are used: lattice phonon Raman and IR spectroscopy. The bulk crystal and substrate‐induced phase have an entirely different molecular packing, and therefore, their Raman spectra are characteristic fingerprints of the respective polymorphs. These spectra can be unambiguously assigned to the individual polymorphs. Drop‐cast and spin‐coated thin films on solid substrates are investigated in the as‐prepared state and after solvent‐vapor annealing. Because Raman spectroscopy is less sensitive with decreasing film thickness, IR spectroscopy is shown to be a more feasible tool for phase detection. The surface‐induced phase is mainly present in the as‐prepared thin films, whereas the bulk phase is present after solvent‐vapor annealing. This result suggests that the surface‐induced phase is a metastable polymorph.