Fluorinated Poly(p-phenylenevinylene)s: Synthesis and Optical Properties of an Intriguing Class of Luminescent Polymers (original) (raw)
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Synthesis of Poly(arylenevinylene)s with Fluorinated Vinylene Units
European Journal of Organic Chemistry, 2008
Poly(arylenevinylene) polymers bearing fluorine atoms in the vinylene units were obtained by a Stille cross-coupling reaction of (E)-(1,2-difluoro-1,2-ethenediyl)bis(tributylstannane) with diiodoaryl derivatives. The introduction of fluorine atoms on the double bond of the stannane leads to polymers with relatively high molecular weights. Furthermore, the presence of fluorinated vinylene units changes the optical properties of the polymers and shifts the emission towards
Journal of Molecular Catalysis A: Chemical, 2000
In this paper, we report on the synthesis of poly phenylenevinylene s containing m-linked phenylene groups in order to reduce the length of conjugation, which is an important tool to influence the color of photo-and electroluminescence. Various substituted and unsubstituted divinylbenzenes and 4,4 X-divinylbiphenyl were synthesized as monomers. These Ž. were polymerized via diene metathesis condensation, acyclic diene metathesis ADMET , using the fluorinated Schrock-type w Ž .Ž Ž. .Ž Ž. . x Ž. Ž. initiator Mo 5NAr 5C H CMe OCMe CF ; Ar s 2,6-diisopropyl-phenyl. The neat poly phenylenevinylene s suf-3 3 2 2 fer from a very low solubility. To overcome this problem, substituents were introduced into the monomers, and copolymerization was performed with exo,exo-norbornene-2,3-dioldiacetate. The polymers were characterized by 1 H-NMR, Ž. FT-IR, UVrVIS and GPC analysis. Photoluminescence PL spectra were taken and used to evaluate the photophysical properties of the oligomers and copolymers, which showed solid-state PL-quantum efficiencies of up to 52%.
Polymer, 2008
This study is an investigation on the interplay between supramolecular organization and optical properties of thin films of conjugated polymers with fluorinated vinylene units such as poly[2-(2-ethylhexyloxy)-5-methoxy]-1,4-phenylenedifluorovinylene (MEH-PPDFV) and poly(2-methoxy-5-propyloxysulfonatephenylenedifluorovinylene) (MPS-PPDFV), which are both PPV polymers with fluorinated double bonds with alkoxy chains in the 2 and 5 positions. MEH-PPDFV is the fluorinated version of the widely investigated MEH-PPV, and MPS-PPDFV is characterized by the presence of ionic alkoxy side chains. This interplay is elucidated exploiting atomic force microscopy, spectroscopic ellipsometry and photoluminescence to obtain complementary information. It is demonstrated that the presence of F-atoms in the vinylene units of the MEH-PPDFV yields a blue optical band gap with the maximum of the fundamental HOMO-LUMO transition and of the room temperature photoluminescence at 3.74 eV (331 nm) and at 2.71 eV (458 nm), respectively. The blue-absorption and emission in the thin films are ascribed to the fact that fluorine atoms on the vinylene units prevent p-stacking of polymeric chains.
Chemistry of …, 2005
A novel conjugated polyfluorene/poly(p-phenylenevinylene) copolymer containing the pendant bis(4alkoxyphenyl) groups in the C-9 position of every alternating fluorene unit has been synthesized and well structurally characterized. The photoluminescence spectrum of this polymer exhibits strong concentration and excitation wavelength dependence in solution. The excited triplet-state maximum of polymer occurs in the region of 460-540 nm with a lifetime of 65.8 µs. This copolymer displays a minor positive nonlinear absorption at the focus of the laser irradiation, suggesting possible reverse saturable absorption. The stable electroluminescent spectrum of the polymer light-emitting diode device based on this copolymer (device configuration, indium-tin oxide/Au/copolymer/LiF/Al) was obtained with a peak wavelength of 515 nm. The bright-green emission observed over the whole active area of the copolymer closely resembles the photoluminescence of the most concentrated solution (0.5 M) used. This suggests that chain stacking in the solid state is responsible for the observed green electroluminescence.
Journal of Physical Chemistry C, 2008
This study deals with the effect that the incorporation of 2,7-fluorenone into the polymer backbone of a poly(fluorenylene-vinylene) exerts on its photophysical properties. The synthesis of a series of random poly(fluorenylene-vinylene)s containing fluorenone at 10, 5, 3, 1% mol/mol ratio with respect to fluorene units (PFVK1-4) was achieved by the Suzuki-Heck reaction cascade between potassium vinyl trifluoroborate and the equivalent quantity of the suitable feed of the corresponding dibromoaryl comonomers in different ratios. The polymers were characterized by 1 H NMR, IR, TGA, DSC, cyclic voltammetry, and UV-vis as well as stationary and time-resolved PL both in solution and in the solid state. In chloroform solution, PFVK1-4 show an emission originating from the PFV backbone while no fluorenone emission could be detected. Moreover, the presence of fluorenone lowers the efficiency quantum yields that inversely follow the fluorenone/fluorene ratio. Conversely, in the solid state, a complete energy transfer occurs and fluorenone acts as the only luminophor even in PFVK1, containing it only in 1% amount respect to fluorene. Consequently, in the solid state PFVK1-4 are all yellow-orange emitters in the solid state. The yellow-orange fluorescence of the obtained polymers in the solid state was compared to the optical behavior of the monodispersed compound 2,7-distyrylfluorenone (DSF). The analysis of the fluorescence decay pathways of the molecules suggests that, differently from DSF, the low-energy emission in the polymers does not originate from a cofacial interaction between fluorenones units. On the contrary, in addition to the fluorenone emission, complex interactions between the fluorenone luminophors and the poly(fluorenylene-vinylene) matrix have to be taken into account for a rationalization of the photophysical properties of these fluorenone-containing polymers in the solid state. Notwithstanding the presence of carbonyl-containing units, usually considered deleterious for the emission properties of poly(arylene-vinylene)s, PFVK1-4 show potential as emitting layers in yelloworange OLEDs, exhibiting luminances up to 1387 cd/m 2 and current efficiencies as high as 0.15 cd/A.
European Polymer Journal, 2011
New conjugated polymers based on separated PPV-type chromophores and incorporating different types of solubilizing side-groups (ethoxy: P1, hexyloxy: P2, dodecyloxy: P3 and benzyloxy: P4) were synthesized via Wittig polycondensation, using a series of bisphenol A-derived di(triphenylphosphonium) salts as starting monomers. The polymers are soluble in common organic solvents and their structures were confirmed by 1 H NMR, 13 C NMR and FTIR spectroscopies. The optical properties of these materials were investigated by UV-vis absorption and fluorescence spectroscopies. In dilute solution, quasi-identical fluorescence spectra were obtained and all the polymers showed a blue emission (420, 445 nm) and a narrow spectrum. In thin solid films, the polymers show side-group-dependent optical behavior and, whereas the emission remains blue in the case of P2, P3 and P4, a green fluorescence was observed for the ethoxylated polymer P1. From cyclic voltammetry analysis, the electrochemical band gaps were estimated to be 2.99, 3.07, 3.15 and 3.06 eV for P1, P2, P3 and P4, respectively. Single-layer diode devices of the [indium tin oxide/polymer/aluminum] configuration have been fabricated and show relatively low turn-on voltages between 2.6 and 4.9 V.
Synthesis and optical properties of oligo- and poly(2,5-dialkoxy-1,4- para-phenylenevinylene)s
Synthetic Metals, 1995
Model compounds based on 1,4-distyrylbenzene and its 2,5-dialkoxy derivatives were synthesized by the Wittig and Wittig-Horner methods. Corresponding poly (2,5-dialkoxy-1,4-para-phenylenevinylene) s (DAPPVs) were obtained from their 2,5-bis (chloromethyl) benzene monomers. The photophysical behavior of the model compounds and DAPPVs was investigated through absorbance, excitation and fluorescence spectroscopy. The absorbance and fluorescence spectra of DAPPVs are red shifted in comparison to the corresponding three-and fivering model compounds by 4600 and 7000 cm-1, respectively. We also report the fluorescence excitation and emission spectra of the model compounds deposited as solid films on quartz and as solid solutions in poly(methyl methacrylate) (PMMA). The photophysical properties of these materials are interpreted from their capacity to form excimer-like molecular dimers. The fluorescence excitation spectra of DAPPV solutions are concentration dependent. We show evidence for the existence of fluorescent aggregates in the solid state,