Poly(pyridinium salt)s with stilbene or distyrylbenzene chromophores

A new series of poly(pyridinium salt)s that contained side stilbenyl groups or p‐distirylbenzene segments in the main chain were synthesized from the reactions of bis(pyrylium salts) with diamines. They were characterized by viscometry, Fourier transform infrared spectroscopy, NMR, X‐ray scattering, differential scanning calorimetry, thermomechanical analysis, ultraviolet–visible analysis, and luminescence spectroscopy. The polymers were amorphous and soluble in polar aprotic solvents such as dimethylacetamide, dimethylformamide, and dimethyl sulfoxide. The glass‐transition temperatures were in the range of 59–123 °C. These polymers had initial decomposition temperatures of 240–295 °C and afforded anaerobic char yields of 29–53% at 800 °C. Both the absorption and photoluminescence (PL) spectra of the polymers were studied, and the PL quantum yields in solution were determined. The polymers showed violet‐blue fluorescence in solution with PL maxima at 408–416 nm and violet‐green fluorescence in thin film with PL maxima at 454–523 nm. The structure of the diamine utilized for the preparation of the polymers did not influence their PL maxima. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2454–2462, 2001     

New poly(p‐phenylene vinylene) derivatives with two oxadiazole rings per repeat unit: Synthesis,photophysical properties,electroluminescence, and metal ion recognition

Two new poly(p‐phenylene vinylene) derivatives OX1‐PPV and OX2‐PPV bearing two 1,3,4‐oxadiazole rings per repeat unit and a fully conjugated backbone with solubilizing dodecyloxy side groups were synthesized and investigated. The amorphous conjugated polymers had glass‐transition temperature values of 60–75 °C and emitted intense blue or greenish‐blue light in solution with photoluminescence (PL) emission maxima at 379–492 nm and PL quantum yields of 0.41–0.52. In the solid state they emitted yellowish‐green light with PL emission maxima at 533–555 nm. Cyclic voltammetry showed that both conjugated polymers had reversible reduction and irreversible oxidation, making them n‐type materials. The electron affinity of OX2‐PPV was estimated as 2.85 eV whereas that of OX1‐PPV was 2.75 eV. Yellow electroluminescence (EL) was achieved from single‐layer light‐emitting diodes of OX2‐PPV with an EL emission maximum at 555 nm and a brightness of 70 cd/m². Polymer OX2‐PPV, which was functionalized with 2,6‐bis(1,3,4‐oxadiazole‐2‐yl)pyridine, demonstrated sensitivity to various metal ions as a fluorescence‐mode chemosensor. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2112–2123, 2004     

Olive oil microemulsions: enzymatic activities and structural characteristics

Microemulsions composed of olive oil, either extravirgin (EVOO) or refined (ROO), as the continuous oil phase, water as the dispersed phase, and a mixture of lecithin-propanol as the emulsifier were prepared and investigated as potential biocompatible media for biotransformations. The area of the microemulsion zone increased considerably by increasing the lecithin to propanol weight ratio in both EVOO- and ROO-based systems. However, the nature of the oil used does not seem to affect the ability of the system to incorporate water. The catalytic activities of two oxidizing enzymes that have been detected in virgin olive oil, namely, tyrosinase and peroxidase, and the activity of a proteolytic enzyme such as trypsin were studied in olive oil microemulsions. In all cases a reduced catalytic activity was observed when ROO was considered as the continuous oil phase. The interfacial properties of lecithin layers were studied by electron paramagnetic resonance spectroscopy employing the nitroxide spin probe 5-doxylstearic acid. By varying the weight ratio of lecithin to propanol and the water content of the microemulsions, the mobility of the probe and the rigidity of the interface were altered. Droplet sizes were measured by dynamic light scattering. At higher water content of the system the size of the droplets was increased. When EVOO was considered as the oil phase, smaller aqueous droplets were formed. Lecithin-based olive oil microemulsions were also characterized with regard to the phenomenon of electrical percolation. At a water content above 3% (w/w) and a lecithin/propanol weight ratio of 2, a sharp increase in conductivity was observed, indicating a structural transition in the bicontinuous form.     

Metabolic Labeling of Sialic Acids in Living Animals with Alkynyl Sugars

Sialome sweet sialome : As sialic acids are involved in many host–pathogen recognition events and are markers of embryonic and malignant tissues, there is great interest in methods for the enrichment and identification of sialylated glycoproteins from complex tissues. Now N‐(4‐pentynoyl)mannosamine can be used to metabolically label sialylated glycoproteins in living animals, enabling future identification of new biomarkers.

     

Femtosecond transient reflection from polymer surfaces during femtosecond UV photoablation

A subpicosecond KrF laser system (248 nm, 0.5 ps) was used as a light source for ablation of PMMA Mylar and Kapton. The time-dependent reflectivity of the light-induced plasma mirror as measured by 496 nm, 0.5 ps long probe pulses showed an increase of up to 94% with 0.4–1 ps rise time and 10–15 ps fall time. The highdensity plasma mirror shows perfect optical quality, and seems to be a promising light-controlled ultrafast switch for UV and visible light. The spectrum of the UV light reflected from the ablated spot is blue shifted by 0.5 nm and shows 1 nm broadening.     

Lecithin organogels used as bioactive compounds carriers. A microdomain properties investigation

Organogels were obtained by adding small amounts of water to a solution of lecithin in organic solvents. Either isooctane or isopropyl palmitate and isopropyl myristate were used as the continuous organic phase of the gels. EPR spectroscopy using both DSA membrane-sensitive and lipophilic spin probes was applied to define the dynamic structure of the surfactant monolayer and the continuous oil phase of lecithin organogels. It was found that by increasing the water quantity, an increase of the polar head area per lecithin molecule was induced, and as a consequence the total interface expanded. It was found that the use of esters as organic solvents induced a decrease of the size of the dispersed structures. The interconnection of the aqueous microdomains and their dynamics were monitored by both static and time-resolved fluorescence quenching spectroscopy using Ru(bipy)32+ as fluorophore and Fe(CN)63- as quencher. It was found that the rates of inter- and/or intra-micellar exchange of water molecules were very slow because they appeared quite immobilized close to the lecithin polar heads. According to the results of the dynamic studies, appropriate organogels were formulated and used to incorporate model bioactive compounds with medicinal or cosmetic interest such as caffeine and theophylline. When these systems were tested for trans-membrane diffusion, they showed a 24 h permeation of 20% and 35%, respectively.     

Proteolytic activity in various water-in-oil microemulsions as related to the polarity of the reaction medium

The catalytic behaviors of α-chymotrypsin and of trypsin were studied in anionic AOT-isooctane-water and cationic CTAB-ROH-isooctane-water microemulsion systems. The effects of various parameters, such as the pH and the water content expressed in terms of the molar ratio w_o = [H₂O]/[Surfactant], on the enzyme activity, were examined. The kinetic constants were calculated and it was found that in the case of trypsin the enzyme exhibited a remarkable “superactivityrd, when studied in the CTAB microemulsion systems. The effect of the alcohol cosurfactant used in these cationic systems was investigated in relation to the polarity of the reaction medium. By using the hydrophilic probe 1-methyl-8-oxyquinolinium betaine the micropolarity of the water core was determined and related to the kinetic results.     

Analyticity for Kuramoto–Sivashinsky‐type equations in two spatial dimensions

I. Stratis In this work, we investigate the analyticity properties of solutions of Kuramoto–Sivashinsky‐type equations in two spatial dimensions, with periodic initial data. In order to do this, we explore the applicability in three‐dimensional models of a spectral method, which was developed by the authors for the one‐dimensional Kuramoto–Sivashinsky equation. We introduce a criterion, which provides a sufficient condition for analyticity of a periodic function u∈C^∞, involving the rate of growth of ?ⁿu, in suitable norms, as n tends to infinity. This criterion allows us to establish spatial analyticity for the solutions of a variety of systems, including Topper–Kawahara, Frenkel–Indireshkumar, and Coward–Hall equations and their dispersively modified versions, once we assume that these systems possess global attractors. Copyright © 2015 John Wiley & Sons, Ltd.     

Transport of alkali-metal picrates through liquid membranes: Coupled action of w/o microemulsion droplets and lipophilic crown-ether carriers

The transport of potassium and sodium picrates is measured by a liquid membrane technique in the presence of two mobile carriers: water-in-oil microemulsion droplets and lipophilic crown-ethers. The fluxes are compared for two cases: (i) the crown-ether (dicyclohexano-18-crown-6 is assumed to be independent of the microemulsion droplet and (ii the crown-ether (dodecano- 18-crown-6) is assumed to be anchored in the droplet. A lower flux is observed when the microemulsion droplet and the crown-ether diffuse as a single entity. These results suggest that larger synergistic effects are obtained when the extractant can diffuse independently of the microemulsion droplet.