Novel low‐band gap alternating copolymers consisting of 9,9‐bis(2‐ethylhexyl)fluorene and 4,6‐di(2‐thienyl)thieno[3,4‐c][1,2,5]thiadiazole and its 3,3″‐dialkyl derivatives were synthesized by Suzuki copolymerization reaction, and their photophysical and electrochemical properties were studied. The copolymers possess small optical band gap 1.3–1.4 eV. The absorption covers the whole visible spectral region. The long‐wavelength absorption maxima in thin films located at approximately 750–785 nm are significantly red shifted compared with those in solution, indicating strong intermolecular interactions. The introduction of alkyl chains to the thiophene units increases the molecular weights of soluble fractions and solubility of the final copolymers, leading to the improved processability of thin films. Polymer solutions exhibited solvatochromism and thermochromism, which is strongly supported by the involvement of the alkyl chains. The copolymers exhibited ambipolar redox properties and reversible electrochromic behavior. The electronic properties are influenced only slightly by alkyl substituents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2743–2756, 2010

The objective of this study was to further evaluate the hypothesis that the accumulation of thiazine dyes, such as methylene blue, by cultured bovine pulmonary arterial endothelial cells involves reduction on the cell surface, followed by diffusion of the lipophilic reduced form of the dye into the cells and intracellular reoxidation to the relatively membrane-impermeant hydrophilic form. The specific question addressed was whether inhibition of methylene blue uptake by cyanide and azide is via inhibition of extracellular reduction or inhibition of intracellular reoxidation. We used the cell membrane-impermeant ferricyanide ion as a secondary electron acceptor to measure the extracellular reduction of methylene blue independently from its uptake by the cells. In addition, toluidine blue O, incorporated into an acrylamide polymer so that it could not permeate the cells in either its reduced or oxidized forms, was used to examine the effects of cyanide and azide on the extracellular reduction. Microscopic observations of the effect of the inhibitors on the intracellular accumulation of methylene blue were also made. The results indicate that the reduction and intracellular sequestration are separate processes and that, in doses that inhibited intracellular reoxidation, and therefore uptake and sequestration, neither cyanide nor azide had an inhibitory effect on extracellular reduction. The intracellular distribution of the observable oxidized form of the dye was consistent with oxidation of the reduced dye within subcellular organelles. The demonstration that extracellular reduction and intracellular sequestration are separate events is consistent with the hypothesized sequence of events.

The binding properties of trivalent ions to polyacrylate and its low molecular weight analogs (monomer, dimer, and trimer) were investigated in dilute aqueous solution (10-2−10-3 M) using Tb3+ ion as a fluorescent probe. The fluorescence intensity and lifetime of the Tb3+ ion depend directly on the number of water molecules bound to their inner coordination sphere. The more efficiently ligands coordinate to Tb3+ ion, the more water molecules are expelled and, consequently, the greater the fluorescence intensity and lifetime observed. Lifetime measurements in H2O and D2O showed that the number of water molecules coordinated to the Tb3+ ion are 6.5, 6.1, 4.9, and 3.6 for monomer, dimer, trimer model compounds, and polyacrylate, respectively. The viscosities of Tb3+−polyacrylate complexes were measured in the presence of a large excess of sodium bromide. Viscosities (ηsp/c) of the polyacrylate solutions follow Huggins' equation, and on addition of Tb3+ ion, the intrinsic viscosities decrease abruptly from 700 to 40 mL/g. The mean end-to-end distances, 〈r 2〉1/2, for polyacrylate in Tb3+−polymer complexes were calculated using the Flory−Fox equation and were found to be reduced from 125 to 48 nm on addition of Tb3+. These results indicate that of the nine water molecules coordinated to Tb3+ ion in aqueous solution, five to six are replaced with carboxylate groups attached to the polymer chain wrapped around the Tb3+.

A new one-step synthesis of formylated poly[methyl(phenyl)silanediyl] (PMPSi) is reported. The aldehyde groups were incorporated into the parent polymer by the reaction with dichloromethyl methyl ether in the presence of Lewis acid (SnCl4). The reaction takes place via an unstable aryl(methoxy)methyl chloride intermediate. The new procedure is an important simplification of the known four-step synthesis of the poly[(formylphenyl)methylsilanediyl] via chloromethylation in the first step. The presence and reactivity of aldehyde groups in the polymer were proved by means of 1H NMR, UV−vis, and FT IR spectroscopies. The reduction in relative molecular weight of the parent polysilane after reaction was not so pronounced as in the multistep synthesis. Model compounds N-benzylidene-1-aminopyrene, N-benzylidene-4-phenylaniline, and N-benzylidene-4-phenylazoaniline were synthesized for spectral characterization of the substituted polysilanes. The π-conjugated systems (pyrene, biphenyl, azobenzene) were attached to the σ-conjugated polysilane backbone. Photophysical properties, photostability, charge photogeneration, and photoluminescence of these materials were studied. Single- and double-layer light-emitting devices (LEDs) with emission in visible spectral region were fabricated. Their spectral and electrical characteristics were studied. Electroluminescence efficiency in double-layer LEDs reached the value of 0.03−0.06% and was more than 1 order of magnitude higher than that in single-layer devices (∼0.005%). Modified polysilanes exhibited better photostability than PMPSi and are particularly intended for the use in multilayer or blend devices.

Three new poly(p‐phenylenevinylene)‐based polymers containing two 1,3,4‐oxadiazole moieties in the main chain per repeat unit were synthesized by Heck coupling. A single, double, or triple bond was introduced between the oxadiazoles to provide a means for modifying the polymer properties. The polymers were readily soluble in common organic solvents and showed Tg values lower than 50 °C. The color of the emissive light in both the solid state and the solution could be tuned by a change in the nature of the bond between the oxadiazole rings. The polymers emitted ultraviolet‐green light in solution with a photoluminescence (PL) emission maximum at 345–483 nm and blue‐green light at 458–542 nm in thin films. The PL quantum yields in solution were 0.36–0.43. The electrochemical properties are affected by the nature of the bond between the oxadiazoles as well. In polymers with a single bond between the oxadiazoles, a lower ionization potential was observed than in polymers with a double or triple bond. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3079–3090, 2005