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The microphase structure in blends of poly(n-butyl methacrylate-co-styrene) (nBMAS) and polystyrene (PS) was investigated by nonradiative energy transfer (NRET) using both steady-state fluorescence and time correlated single-photon counting (TCSPC) measurements. The nBMAS was labeled with anthryl groups by semicontinuous emulsion copolymerization. Studies of the morphology and phase separation of these blends performed by epifluorescence microscopy were complemented by differential scanning calorimetry. Miscibility of polymers with several compositions, from 5 to 95% w/w, was studied. For compositions with PS < 80 wt % we obtained a partial miscibility with discrete domains of PS dispersed in a nBMAS matrix. Blends up to PS = 20 wt % presented a co-continuous morphology whereas a bicontinuous morphology was generated for lower PS content. Fluorescence lifetimes and the lifetime distribution were consistently associated with the microheterogeneity of the material and were considered an additional criterion for the analysis of miscibility.

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...

We describe the employment of steady-state fluorescence spectroscopy coupled to epifluorescence microscopy (fluorescence microspectroscopy) for monitoring the diffusion of the lower-T g component during heating of a binary blend of poly(n-butyl methacrylate-co-styrene) containing 9-vinylanthracene units attached as fluorescent label (nBMAS) with polystyrene. The segregation of the nBMAS was monitored by simply measuring the emission spectra over areas of a few micrometers at 40 °C (above nBMAS-T g) near the interfacial region as a function of time, while the morphological changes and the flux of diffusant were readily revealed during the annealing process. The apparent diffusion coefficient, D ap = (1.6 ± 0.1) × 10-6 cm2 s-1, was extracted from the slope of the better linear fitting from the plot of relative intensities (as integrated spectra) vs t 1/2.