Coating of a lignocellulosic aggregate with pectin/polyethylenimin mixtures: Effects on flax shive and cement-shive composite properties

Lignocellulosic lightweight concretes are a potential contributor to sustainable development. However, lignocellulosic aggregates are not always fully compatible with cement matrices leading to setting delays, significant dimensional variations and low mechanical strengths. An aggregate treatment, reducing water absorption and water-soluble molecule release, can avoid or reduce these drawbacks. In this study a coating treatment, using a pectin/polyethylenimin (PP) mixture, was applied to flax shives, which is a lignocellulosic by-product. Before shive coating, a dilution with distilled water or a micro-wave heating were conducted to decrease PP mixture viscosity.The PP treatment involved a decrease in shive water absorption. Compared to standard shive concrete, treated shive concrete exhibited a decrease in setting delay with an increase in cement hydration enthalpy, an increase in mechanical strengths and a significant reduction in dimensional variations. Although a slight increase in thermal conductivity and bulk density was measured, the cement-shive composite obtained still belongs to the insulating concrete category.     

Electropolymerization of N-methylanthranilic acid and spectroelectrochemical characterization of the formed film

The electropolymerization of N-methylanthranilic acid (NMAA) is reported in this paper. The monomer is substituted both at ortho- and N-position and, to the best of our knowledge, it has not been previously electropolymerized. Electropolymerization of NMAA was done on glassy carbon and optically transparent (indium) tin oxide electrodes. The obtained films, which are probably of an oligomeric nature (oligoNMMA), were characterized with cyclic voltammetry (CV), in situ UV–vis and Raman spectroscopy, ex situ FTIR spectroscopy and scanning electron microscopy (SEM).Our results show that NMAA can be electropolymerized as thin films in 1.0 M HClO₄, but the oxidation and reduction peak currents in the CVs indicate that the formed oligoNMAA films are thinner than poly(N-methylaniline) or poly(N-butylaniline) films prepared under similar conditions. The CV and UV–vis measurements confirm that oligoNMAA have three oxidation states like suggested in the redox scheme of substituted polyanilines. The Raman spectra of oligoNMAA also verify that more quinoid units are formed at higher potentials in accordance with the redox scheme. The ex situ FTIR measurement proves that covalently attached carboxylic acid groups are present in the film structure and attached to the oligoNMAA backbone.     

Influence of charged tail groups of self-assembled monolayers on electrodeposition of polyaniline

Self-assembled monolayers (SAMs) of thiols with three different tail groups, −COOH, −SO₃Na, and −NH₂, were used to modify the Au substrates for electrodepositing polyaniline (PANI). Electrochemical quartz crystal microbalance (EQCM) results indicated a slower rate of deposition of PANI on a SAM surface consisting of positively charged amine groups compared to polymerization on bare gold and on a SAM of carboxyl acid groups. The properties of the SAM layers are dependent on the pH value of the solutions, and are effective only at very low pH values (pH < 2). A layer of the positively charged amino groups in acidic solution acted as a barrier for electron transfer in electro-oxidation of aniline monomer. The positively charged SAM of amine groups also increased repulsion between the coupled aniline species and the electrode surface and in this way hindered electrodeposition. Modification of the surface with pre-patterned SAMs have been demonstrated to be a convenient and practical way to fabricate selectively deposited thin films of polyaniline.     

An apparatus for the comparative collection of headspace volatiles of watercress

An apparatus is described for the collection of headspace volatiles from comparative samples of watercress in controlled temperature and lighting conditions by adsorption on Porapak Q. Gas chromatographic and mass spectrometric analysis of the volatiles from green watercress with and without a cytokinin treatment, and green and Florida type watercress were compared over a 7-day period at 10°C in the dark.     

The examination of the headspace volatiles of watercress

Watercress volatiles were collected by adsorption on Porapak Q and solvent elution to obtain samples representative of the intact plant material with minimum glucosnolate degradation. Samples taken after 2 and 7 days trapping as the watercress deteriorated were compared. Several compounds which contribute to the aroma of watercress were identified by gas chromatographic and mass spectrometric analysis and odour evaluation of the gas chromatographic effluent.     

Study of electrolyte effects on electrochemical synthesis and p-doping of poly(thienyl biphenyl) films

The electrochemical synthesis and charging–discharging process of a copolymer consisting of 3-octylthiophene (3-OT) and biphenyl units have been studied in different electrolytic media. The polymer material has been characterized by electrochemical and spectroscopic methods: cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), chronopotentiometry, chronoamperometry and FTIR spectroscopy. The diffusion coefficients of different ions in poly(thienyl biphenyl) (PTB) films have been determined by chronoamperometry and compared with corresponding values in poly(3-octylthiophene) (POT) and poly(paraphenylene) (PPP). The best electrolytic conditions for synthesis of poly(thienyl biphenyl) concerning the copolymer structure was found to be in 0.1 M lithium hexafluoro arsenate (LiAsF₆) in acetonitrile. In this electrolyte solution, the content of phenylene segments compared to thienylene segments is highest resulting in a higher degree of cross-linking compared with films made in the presence of the other electrolyte salts studied.     

Simultaneous monitoring of the transport of anions and cations across polypyrrole based composite membranes

A mechanism for the macroscopic charge balance during the transport of anions and cations across polypyrrole based composite membranes is proposed. For the mechanism to be studied, anions and cations were monitored simultaneously across PPy based composite membranes, which are known to have cation exchange (PPy(PSS)), anion exchange (PPy(ClO₄)) and mixed ion exchange properties (PPy(pTS)). Even though none of the membranes were found to be completely permselective, the flux of cations was higher than that of anions across the PPy(PSS) composite membrane, while the flux of anions was higher than that of cations across the PPy(ClO₄) composite membrane. Distinct changes in pH of the receiving solution were also observed. These were a decrease in pH when a predominantly anion exchanging polypyrrole composite membrane was used, and an increase in pH when a membrane that maintains charge balance principally by cation exchange was used. When membranes which display approximately equal permeability towards anions and cations were used the pH of the receiving solution was ca. 6–8. There was only a negligible flux of Ca²⁺ across the PPy(PSS) membrane in the transport experiments carried out with the source solution consisting of either Ca(NO₃)₂ or an equimolar mixture of KNO₃ and Ca(NO₃)₂. The PPy(PSS) composite membrane was impermeable towards NO₃⁻ ions when the source solution was Ca(NO₃)₂ but permeability towards NO₃⁻ was observed when the source solution was either KNO₃ or an equimolar mixture of KNO₃ and Ca(NO₃)₂.     

Effect of macerating enzyme treatment on the polyphenol and polysaccharide composition of red wines

Effect of macerating enzymes on the polyphenol and polysaccharide composition of Merlot wines after 20 months of ageing was studied over three vintages (2004, 2005, 2006). Pectinase rich enzyme preparations, by degrading grape berry cell walls, led to a modification of the molecular weight distribution of polysaccharides released into the wines. Enzyme-treated wines contained more Rhamnogalacturonan II (RG-II) and less polysaccharides rich in arabinose and galactose (PRAGs) over the three vintages. The enzyme treatment also modified wine polyphenol composition. An increase of colour intensity, of derived pigments resistant to sulphite bleaching and of proanthocyanidins (condensed tannins) was observed, modulated by vintage effect. Principal Component Analysis of all the data indicated both vintage and enzyme effects. Beside the vintage effect separating the wine samples, the impact of enzyme treatment on wines was established for each year.     

Electrochemical polymerization and characterization of a poly(azulene)-TiO<Subscript>2</Subscript> nanoparticle composite film

A poly(azulene)-TiO₂ composite film (PAz-TiO₂) was synthesized electrochemically by oxidation of azulene in an electrolyte medium containing TiO₂ nanoparticles. Polymerization was performed under magnetic stirring in an acetonitrile solution containing tetrabutylammonium hexafluorophosphate as the electrolyte salt. Influence of the concentration of TiO₂ in the reaction suspension on the electrochemical and optical properties and on the structure of the composite films was studied by cyclic voltammetry, ex situ Raman and FTIR reflection spectroscopy and in situ UV–vis and FTIR spectroelectrochemical techniques. Morphology of the composite films was studied by Scanning Electron Microscopy and the amount and distribution of the TiO₂ nanoparticles within the polymeric matrix by Inductively Coupled Plasma Mass Spectrometry with laser ablation. Addition of TiO₂ in the reaction suspension had a small catalytic activity for the polymerization of Az. Inclusion of TiO₂ nanoparticles in PAz did not affect the voltammetric behavior or the chemical structure of the formed polymer films. However, a different chain conformation and morphology of the film was formed when synthesized in presence of TiO₂ compared to the plain PAz film. It was also found that the film morphology was more homogeneous when the concentration of TiO₂ was ≥10 mM in the polymerization solution than films polymerized without any TiO₂.     

Simultaneous LC-MS/MS determination of reference pharmaceuticals as a method for the characterization of the Caco-2 cell monolayer absorption properties

Since its introduction a decade ago, the Caco-2 in vitro model for testing intestinal permeability has found wide application, in particular for screening new molecules in the pharmaceutical industry. An important issue for the validation of the model is to verify integrity and proper functionality of the Caco-2 cells monolayer, to ensure reproducibility and consistency of results. Several of these methods are based on measuring the apparent permeability coefficients (Papp) of well-characterized reference compounds, having known absorption characteristics, and comparing the observed values to those expected. Most of them use fluorescent or radioactive chemicals to test different parameters. The main limitation of such approaches is that each parameter to be tested is associated with a single specific method, so that multiple procedures are needed to adequately characterize the cell monolayer. This work describes the use of a unique LC-MS/MS method to simultaneously determine the Papp of a set of reference substances having well-characterized absorption behavior, i.e., phenylalanine, atenolol, and propranolol. The method is routinely used in our laboratory to check on model reproducibility and proved useful in verifying the consistency of the results derived from the experiments.