Probing interchain interactions in emissive blends of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene] with polystyrene and poly(styrene-co-2-ethylhexyl acrylate) by fluorescence spectroscopy

Abstract

Nesse trabalho foram realizados estudos dinâmicos e estáticos de fotoluminescência de blendas poliméricas do poli[2-metóxi-5-(2'-etilexiloxi)-p-fenileno vinileno] (MEH-PPV) com poliestireno-co-2-co-metacrilato de metila1-1-pirenila e seu copolímero poli(estireno-co-acrilato de 2-etilexila-co-1-metacrilato de metila1-1-pirenila) (com 9 mol% e 19 mol% de unidades acrilato de 2-etilexila unidades e 0,06 mol% de 1-pirenila). O poliestireno marcado com pirenilo e alguns de seus copolímeros foram sintetizados por polimerização em emulsão e caracterizados por 13 C e 1 H NMR, FTIR, GPC, DSC e UV-Vis. Os filmes foram preparados por deposição centrífuga a partir de soluções em clorofórmio, sendo a composição das blendas de 0,1, 0,5, 1,0, e 5,0 m/m% de MEH-PPV. A miscibilidade desses sistemas foi estudada através dos processos de transferência não-radiativa de energia entre o grupo 1-pirenila (doadores de energia) e o MEH-PPV (receptor de energia). A intensidade relativa de emissão e os tempos de decaimento de fluorescência do doador mostraram que a miscibilidade do MEH-PPV e dos copolímeros e maior do que entre o MEH-PPV e o poliestireno o que foi confirmado por microscopia óptica de epifluorescência e por microscopia eletrônica de varredura.We present dynamic and static photoluminescence studies on polymer blends of conjugated poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) with polystyrene-co-1-pyrenyl methyl methacrylate and its copolymer poly(styrene-co-2-ethylhexyl acrylate-co-1-pyrenylmethyl methacrylate) (with 9 mol% and 19 mol% of 2-ethylhexyl acrylate units and 0.06 mol% of 1-pyrenyl). Pyrenyl-labeled polystyrene and its copolymers were synthesized by emulsion polymerization and characterized by 13 C and 1 H-NMR, FTIR, GPC, DSC, and UVVis. Spin-coating films of the blends were prepared from chloroform solutions with 0.1, 0.5, 1.0, and 5.0 wt% of MEH-PPV. The miscibility of these systems was studied by non-radiative energy transfer processes between the 1-pyrenyl moieties (the energy donor) and MEH-PPV (the energy acceptor). The relative emission intensities and the fluorescence lifetimes of the donor showed that the miscibility of MEH-PPV and the copolymers is greater than that of MEH-PPV and polystyrene and this was confirmed by epifluorescence optical microscopy and scanning electron microscopy.Keywords: poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV), blends, miscibility, copolymer poly(styrene-co-2-ethylhexyl acrylate-co-1-pyrenylmethyl methacrylate), fluorescence, energy transfer IntroductionConjugated polymers are the subject of considerable scientific attention because they constitute attractive components for application as emissive materials in electroluminescent devices and, in particular, as organic light-emitting diodes (OLED).1 Such interest is attributed to their superior processability and flexibility relative to inorganic compounds, greater possibility of preparation of materials with distinct emission colors, electroluminescence emission with low turn-on volt...

Energy Transfer from Poly(Vinyl Carbazole) to a Fluorene‐Vinylene Copolymer in Solution and in the Solid State†

“…PVK in dilute THF solution presented a high concentration of excimers, which also indicates that the chains were not completely extended. Consequently, in terms of dimensions, the R g values of these two polymers are much larger than the Förster radius for FRET that is generally observed for conjugated polymers (3–5 nm; 24,50).…”

“…According to this model, donors and acceptors are point dipoles with weak interactions; furthermore, the Fo¨rster equation for R 0 requires that the FRET process occur under thermally equilibrated conditions (12). In the literature, studies have reported that the Fo¨rster radius for conjugated polymer blends is in the range of 3-7 nm (6,7,11,17,18,25,26,40,50,54). One methodology for the calculation of R 0 takes into account experimental data such as the overlap integral between the donor emission and the acceptor absorption, the refractive index of the medium, the PL quantum yield of the donor in the absence of the acceptor, and an orientational parameter for the dipole distributions (12,22).…”

Electronic Structure and Optical Properties of an Alternated Fluorene–Benzothiadiazole Copolymer: Interplay between Experimental and Theoretical Data

“…Ludox was used as scatterer to register the instrumental response. Deconvolution of the laser pulse was performed, optimizing the random residual distribution to achieve a χ 2 parameter close to unity. , Decays were initially recorded using pulsed diode lasers for excitation (375 and 470 nm) and collected with emission at 550 nm. Experiments of time-resolved emission spectroscopy were performed using the same excitations and tuning the emission from 500 to 700 nm in intervals of 10 nm.…”

Time resolved emission spectroscopy of poly(2,5-dicyano-p-phenylene-vinylene) films

“…10 The study of the electronic excited state dynamics of conducting polymer using excitation and emission spectroscopy has provided important information about exciton diffusion, migration, trapping and quenching in aggregates like excimers or its deactivation in low energy charge-transfer states. [11][12][13][14][15] These processes are closely related to the luminescence yields and stability of several optoelectronic devices based on conjugated polymers.…”