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Raman Spectra of Poly( p ‐phenylenevinylene)s with Fluorinated Vinylene Units: Evidence of Inter‐ring Distortion
Author(s) -
Piacenza Manuel,
Comoretto Davide,
Burger Martin,
Morandi Valentina,
Marabelli Franco,
Martinelli Carmella,
Farinola Gianluca M.,
Cardone Antonio,
Gigli Giuseppe,
Della Sala Fabio
Publication year - 2009
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.200900041
Subject(s) - raman spectroscopy , fluorine , ring (chemistry) , polymer , materials science , planarity testing , oligomer , alkoxy group , photochemistry , chemistry , polymer chemistry , crystallography , organic chemistry , optics , physics , metallurgy , composite material , alkyl
Ring the changes : Experimental Raman spectra of fluorinated and non‐fluorinated polyphenylenevinylenes are assigned according to quantum chemical calculations for oligomer model systems (see picture). Characteristic differences in the spectra can be traced back to strong inter‐ring distortion of the fluorinated compounds.The Raman spectrum of poly{2‐methoxy‐5‐[(2‐ethylhexyl)oxy]‐1,4‐phenylenedifluorovinylene} (MEH‐PPDFV) is reported and compared with that of a well‐known non‐fluorinated reference polymer, namely poly{2‐methoxy‐5‐[(2‐ethylhexyl)oxy]‐1,4‐phenylenevinylene} (MEH‐PPV). The Raman spectra of both polymers are assigned on the basis of density functional theory calculations of the corresponding oligomers. The main differences between vinylene fluorinated and non‐fluorinated structures deal with the intensity, frequency shift and broadening of CC vinylene stretching. Additional differences concern the relative intensities of CC phenylene and vinylene stretching as well as the deformation modes in the range 1250–1350 cm −1 . It is shown that these effects are due to the larger distortion from planarity of the fluorinated polymer, compared with the non‐fluorinated counterpart, induced by repulsive interactions between the fluorine atoms on the vinylene units and the oxygen atoms of the alkoxy groups on the aromatic rings.