A study of the different structural phases of the polymer poly(9,9′-dioctyl fluorene) using Raman spectroscopy

Ariu, M.; Lidzey, David G.; Lavrentiev, M. Yu.; Bradley, Donal D. C.; Jandke, M.; Strohriegl, Peter

doi:10.1016/s0379-6779(00)00456-2

Cited by 58 publications

(50 citation statements)

References 12 publications

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“…8,9 As these phases can be rather selectively maintained via proper selection of processing parameters, 4,8,9 the resulting morphology effects in light-emission properties of PFO have been extensively examined in the literature. [10][11][12][13][14][15][16][17][18][19] However, details of the molecular arrangement in these phases remained obscure, 9,18 rendering earlier attempts to establish a correlation between morphology and photophysical properties rather imprecise. Systematic clarification of the phase behavior of PFO is clearly needed.…”

Section: Introductionmentioning

confidence: 99%

Crystalline Forms and Emission Behavior of Poly(9,9-di-n-octyl-2,7-fluorene)

et al. 2004

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By means of transmission electron microscopy (TEM) and X-ray diffraction (XRD) we demonstrate the presence of a previously unspecified modification (R′) of the crystalline (R) phase in poly(9,9-di-n-octyl-2,7-fluorene) (PFO). The R′ form is metastable and lower in melting temperature than the R form, and its formation is kinetically favored at temperatures lower than 130°C. The modification involves mainly a slight increase in the b axis from 2.34 to 2.38 nm and lowered symmetry along this axis, whereas the a axis tends to lie preferentially normal to film surface. Using specimens composed selectively of R and R′ phases, respectively, we show that films of the two forms are characteristically different in routine 1-D XRD profiles and absorption spectra. These are attributable to the oriented nature of the R′ form as well as minor but significant differences in molecular packing and backbone coplanarity. However, photoexcited emission spectra of these films remain highly similar in the vibronic structure to the purely nematic film, with only minute shifts in emission maxima that are inconsistent with the significantly red-shifted absorption edge upon crystallization. This appears better explained by assuming that the liquid-crystalline matrix rather than crystalline domains dominates optical emission of PFO.

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Section: Introductionmentioning

confidence: 99%

Crystalline Forms and Emission Behavior of Poly(9,9-di-n-octyl-2,7-fluorene)

et al. 2004

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“…Associated vibrational modes provide information on the electron-phonon coupling, [15][16][17] isomerization processes, [18] polymerization kinetics, [19] the presence of different forms or phases, [20][21][22][23] crystallographic phase transitions, [24] polymer regioregularity [25] and the role of conjugation length, [26] one of the most common sour-…”

Section: Introductionmentioning

confidence: 99%

Raman Spectra of Poly(p‐phenylenevinylene)s with Fluorinated Vinylene Units: Evidence of Inter‐ring Distortion

et al. 2009

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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.

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“…For example, in the case of poly (9,9-dioctylfluorene) (PFO), isotropic glassy thin films are obtained by spincoating. By annealing these films at an appropriate temperature, crystalline thin films are obtained [3][4][5][6] with nanocrystals of PFO embedded in the disordered matrix [7].…”

Section: Introductionmentioning

confidence: 99%

“…PFO, whose chemical structure is depicted in Fig. 1, is known to exhibit morphologydependent optical properties [3][4][5][6]. Its glassy thin films show an absorption spectrum similar to that of its dilute solution, whereas in the crystalline state, a characteristic shoulder appears in the low-energy range of the absorption spectrum.…”

Section: Introductionmentioning

confidence: 99%