Raman spectra of poly(p-phenylenevinylene)s with fluorinated vinylene units: evidence of inter-ring distortion.
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.
Piacenza
Manuel
M
National Nanotechnology Laboratory (NNL) of CNR-INFM, Università del Salento, Via per Arnesano, 73100 Lecce, Italy. manuelpiacenza@gmail.com
Comoretto
Davide
D
Burger
Martin
M
Morandi
Valentina
V
Marabelli
Franco
F
Martinelli
Carmella
C
Farinola
Gianluca M
GM
Cardone
Antonio
A
Gigli
Giuseppe
G
Della Sala
Fabio
F