title: Raman spectra of poly(p-phenylenevinylene)s with fluorinated vinylene units: evidence of inter-ring distortion.
abstract: Ring the changes: Experimental Raman spectra of fluorinated and non-fluorinated polyphenylenevinylenes are assigned according to quantum chemical calculations for oligomer model systems [picture: see text]. 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 C--C vinylene stretching. Additional differences concern the relative intensities of C-C 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.
authors.affiliation: National Nanotechnology Laboratory (NNL) of CNR-INFM, Università del Salento, Via per Arnesano, 73100 Lecce, Italy. manuelpiacenza@gmail.com
authors.forename: Manuel
authors.initials: M
authors.lastname: Piacenza
authors.forename: Davide
authors.initials: D
authors.lastname: Comoretto
authors.forename: Martin
authors.initials: M
authors.lastname: Burger
authors.forename: Valentina
authors.initials: V
authors.lastname: Morandi
authors.forename: Franco
authors.initials: F
authors.lastname: Marabelli
authors.forename: Carmella
authors.initials: C
authors.lastname: Martinelli
authors.forename: Gianluca M
authors.initials: GM
authors.lastname: Farinola
authors.forename: Antonio
authors.initials: A
authors.lastname: Cardone
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Gigli
authors.forename: Fabio
authors.initials: F
authors.lastname: Della Sala