Novel biodegradable copolyesters containing blocks of poly(3-hydroxyoctanoate) and poly(epsilon-caprolactone): synthesis and characterization

Novel biodegradable polyester block copolymers have been synthesized by using well-defined poly(3-hydroxyoctanoate) (PHO) oligomers having a hydroxyl end group and an ester end group with M(n) values of 800, 2,500, 5,300, 8,000, or 20,000 as an elastomeric soft segment and poly(epsilon-caprolactone) as a more crystalline segment. These PHO oligomers prepared by methanolysis were subjected to block copolymerization with epsilon-caprolactone. The chemical structure of the copolymers was confirmed by (1)H NMR and (13)C NMR spectroscopy. All the copolyesters are semi-crystalline and two T(g) were observed by differential scanning calorimetry when the molecular weight of the PHO block is about 20,000.     

Nucleophilic trifluoromethylation of aryl halides with methyl trifluoroacetate

When associated with an alkaline halide, such as cesium fluoride or cesium chloride, and Cu(I) species, methyl trifluoroacetate (MTFA) constitutes a valuable trifluoromethylating agent for substituting aromatic (or heteroaromatic) iodides and bromides. The reaction can be carried out in DMF at 180 °C or, better, in sulfolane which allows he reaction to proceed at a lower temperature (from 140 °C).     

Captodative α,β-unsaturated oxazolines as dienophiles in the asymmetric Diels-Alder reaction

Captodative oxazoline derivative 5a gave rise to four-cycloadducts 6, 7, 8 and 9 in the presence of trifluoroacetic anhydride and cyclopentadiene. Hydrolysis of 6 led to α-phenylthio carboxylic acid 14.     

Dynamics of a bilayer membrane with membrane-solvent partial slip boundary conditions

We discuss the dynamics of a bilayer membrane with partial slip boundary conditions between the monolayers and the bulk fluid. Using Onsager’s variational principle to account for the associated dissipations, we derive the coupled dynamic equations for the membrane height and the excess lipid density. The newly introduced friction coe?cients appear in the renormalized fluid viscosities. For ordinary lipid bilayer membranes, we find that it is generally justified to ignore the e?ects of permeation and parallel slip at the membrane surface.     

Evaluation of Energy Balance in a Batch and Circulating Non-thermal Plasma Reactors During Organic Pollutant Oxidation in Aqueous Solution

Plasma Chemistry and Plasma Processing - This work presents the treatment of an organic waste solution using gliding arc plasma in moist air, which is an excellent source of oxidizing species....     

Mass spectral studies of perfluorooctane sulfonate derivatives separated by high-resolution gas chromatography

The mass spectral characteristics of perfluorooctane sulfonate (PFOS, C(8)F(17)SO(3)-) isomers present in technical PFOS were obtained using high-resolution gas chromatography (HRGC) combined with mass spectrometry (MS). To make PFOS amenable to HRGC separation, a simple derivatization procedure was developed. The method involved the conversion of PFOS into the iso-propyl ester using iso-propanol as the derivatization reagent under acidic conditions. Mass spectra were generated employing electron ionization (EI) and negative chemical ionization (NCI). Interpretation of fragment ions was possible due to the use of deuterium-labeled iso-propanol as derivatization reagent, which induced mass shifts in the electron ionization (EI) and negative chemical ionization (NCI) mass spectra. HRMS allowed the accurate mass measurement of important EI fragments and confirmed the derivatization reaction as well as the proposed fragmentation pathway involving rearrangement. Moreover, the high resolution provided by HRGC enabled the separation of eleven PFOS isomers present in the technical product. This is an improvement over the previously reported high-performance liquid chromatography (HPLC) separation. A complete identification of all isomers was not possible due to lack of pure reference materials. Finally, the developed derivatization procedure was successfully applied to perfluoroalkyl carboxylates (PFCA) and corresponding fragmentation involving rearrangement of the derivatized PFCA was observed. The described qualitative derivatization offers a promising alternative technique for the separation and identification of isomers of perfluoroalkyl sulfonates and carboxylates by HRGC/MS.     

Optimisation of pressurised liquid extraction by experimental design for quantification of pesticides and alkyl phenols in sludge,suspended materials and atmospheric fallout by liquid chromatography–tandem mass spectrometry

The study proposes an analytical method to quantify 10 alkylphenols and 12 pesticides at ultra-trace levels by liquid chromatography in reverse mode coupled to positive electrospray ionisation–tandem mass spectrometry. The extraction procedure from environmental solids was optimised by pressurised liquid extraction using acetonitrile:isopropanol (1:1, v/v). The influence of several extraction experimental factors, temperature, pressure, duration and number of cycles, related to the PLE was investigated by an original and efficient chemometric approach. The optimised extraction method (80 °C, 40 bar, 10 min, 1 cycle) exhibited recoveries between 67 and 127% with RSD mostly under 13%. The whole method was applied to real samples: sludge, suspended materials, atmospheric fallouts and roof deposit. Pollutant levels were between 1 μg kg⁻¹ and 5.9 mg kg⁻¹.