Effects of annealing on crystallinity and phase behaviour of PET/PC block copolymers

The effects of the annealing on the properties of PET/PC block copolymers, obtained by reactive blending in the presence of different catalysts and for different mixing times, have been studied. The annealing, performed in conditions that promote the crystallization, has been used to better understand the role of block length in determining the phase behaviour. The copolymers characterized by blocks with molecular weight larger than 8000 are able to reorganize towards more ordered domains. This rearrangement maintains the phase separation, as two crystalline phases are present before and after annealing, due to the immiscibility of long blocks. In copolymers characterized by blocks with molecular weight equal to about 2500, that is the higher limit for the miscibility in the amorphous state in PET/PC block copolymers studied in this work, the rearrangement of the chains during annealing causes a phase separation leading to two crystalline phases. Only in the copolymers with molecular weight of blocks lower than 1500, the very short block length hinders the crystallization: therefore, only in this case a phase separation does not take place after annealing.     

A highly efficient synthetic route to ketones through sequential coupling reactions of grignard reagents with s-phenyl carbonochloridothioate in the presence of nickel or iron catalysts

The sequential coupling reactions of Grignard reagents with $\text{S}$phenyl carbonochloridothioate in the presence of nickel(II) or iron(III) catalysts provides a very mild and straightforward route to symmetrical and unsymmetrical aliphatic and aromatic ketones.     

Simultaneous Determination of Trichothecenes A, B, and D in Maize Food Products by LC–MS–MS

Two new methods of analysis, based on liquid chromatography–tandem mass spectrometry, for simultaneous determination of trichothecenes A, B, and D in maize flour and oil have been developed and validated in accordance with European Commission decision 2002/657/EC (recovery, CCα, CCβ, and precision). The trichothecenes were extracted from maize flour by matrix solid-phase dispersion, with recoveries ≥79%, and from maize oil by liquid–liquid extraction, with recoveries ≥78%. Limits of quantitation ranged between 0.03 and 50 μg kg^?1, depending on the electrospray response to each analyte and on the matrix. Monitoring of flour and oil samples with this HPLC–MS–MS method revealed the presence of deoxynivalenol, T-2 toxin, and diacetoxyscirpenol at very low concentrations.     

Simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene using high-performance liquid chromatography/hybrid quadrupole time-of-flight mass spectrometry

A simple and rapid method using reversed-phase liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the simultaneous determination of the urinary metabolites of benzene, toluene, xylene and styrene in human urine specimens and standard solutions is described. A hybrid quadrupole/time-of-flight (QqTOF) mass spectrometer was compared for the determination of metabolite of aromatic solvents in urine samples. The metabolites selected were: trans,trans-muconic acid, hippuric acid, o-, m- and p-methylhippuric acid and phenylglyoxylic acid. The compounds were well separated from each other on narrow-bore 1-mm i.d. reversed-phase LC C-18 columns. Average recoveries for loading 100 microL of urine samples varied from 88-110% and the quantification limits were less than 30 ng/mL for each analyte (3 ng/mL for trans,trans-muconic acid). The qualitative information obtained (mass accuracy, resolution and full-scan spectra) with the QqTOF mass spectrometer allows a secure identification of analytes in biological matrices.     

Stereoselective total synthesis of (S)-Virol C and (S)-1-dehydroxyvirol A

A stereoselective total synthesis of (S)-Virol C and (S)-1-dehydroxyvirol A has been developed, based upon the selective and sequential substitution of the two trimethylsilyl groups of readily available 1,4-bis(trimethylsilyl)-1,3-butadiyne.     

Promotion of Förster Resonance Energy Transfer in a Saponite Clay Containing Luminescent Polyhedral Oligomeric Silsesquioxane and Rhodamine Dye

A new hybrid photostable saponite clay with embedded donor–acceptor dyes was prepared and characterized in this work. The saponite is intercalated with a luminescent polyhedral oligomeric silsesquioxane, which transfers the photoexcitation energy directly to an acceptor dye (rhodamine B). The obtained composite material was characterized by means of XRD, TEM microscopy, and UV/Vis and photoluminescence spectroscopy. A physicochemical study showed that the system behaved as an efficient Förster resonance energy transfer pair, owing to the very good spectral overlap of donor emission (λ_em=510–540 nm) and acceptor absorption in the λ=530–570 nm range. The hybrid material represents the first example of a photonic antenna based on a synthetic saponite clay and can be considered a step forward in the search for new, efficient, and stable materials suitable for light‐harvesting applications.     

Development of a Xanthine Oxidase Modified Amperometric Electrode for the Determination of the Antioxidant Capacity

This paper describes the development of a xanthine oxidase/poly‐m‐phenylenediamine (XOD‐PPD)‐modified electrode. The biosensor was constructed by encapsulating XOD in a sol‐gel matrix deposited onto a platinum based screen‐printed electrode functionalized with a permselective PPD membrane. The hydrogen peroxide generated as a final product of the enzymatic reaction between the hypoxanthine and the XOD or by the spontaneous dismutation of superoxide radicals was selectively monitored at +700 mV. The use of a highly selective PPD layer blocked the nonspecific oxidation of other oxidizable molecules. Finally the biosensor was applied to the determination of the antioxidant capacity of acetylsalicylic acid.     

Room temperature femtosecond optical parametric generation in MgO-doped stoichiometric LiTaO3

We demonstrate room temperature femtosecond optical parametric generation with high average output power in periodically poled MgO-doped stoichiometric LiTaO₃. Direct pumping with 725-fs pulses from a passively mode-locked thin disk laser at 1030 nm resulted in stable 1.5 W average signal power at 1484 nm at the full laser repetition rate of 59 MHz. With this demonstration we achieved a significant simplification of our recently presented red-green-blue laser source because no temperature stabilization of any nonlinear crystal is required. PACS 42.65.Yj; 42.70.Mp; 42.79.Nv     

Synthesis of α-amino acid derivatives by copper(I)-catalyzed conjugate addition of grignard reagents to methyl 2-acetamidoacrylate

The reactions of Grignard reagents with methyl 2-acetamidoacrylate in the presence of CuI give fair to good yields of α-amino esters; the corresponding α-deutero- or α-methyl-derivatives are obtained upon quenching with D⁺ or CH₃I, respectively.