Synthesis and characterization of imidized poly(styrene‐maleic anhydride) nanoparticles in stable aqueous dispersion

Organic nanoparticles are synthesized by partial imidization of high‐molecular weight styrene(maleic‐anhydride) with 26 to 34 mol% maleic anhydride, in aqueous environment and presence of ammonium hydroxide. The nanoparticle dispersions have a maximum solid content of 35 wt% and good stability that critically depends on the ratio of imidized and ammonolyzed maleic anhydride moieties. The deprotonated residual maleic anhydride moieties provide dispersion stability at pH > 4, while protonation at pH < 4 causes nanoparticle sedimentation. After presentation of the synthesis conditions, the imidization reaction is characterized by FT‐IR and Raman spectroscopy, followed by thermal analysis (TGA, DSC), and morphological characterization (DLS, SEM, TEM, AFM). The reaction conditions were optimized by physical characterization of various dispersions, and finally nanoparticles could be obtained with a maximum degree of imidization of 77% in dispersed conditions, or 90 to 95% after drying that are favorable for coating applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Incorporating different vegetable oils into an aqueous dispersion of hybrid organic nanoparticles

Quantum dots (QDs) are routinely employed for bioimaging applications and detection of pathogens and toxins. Their use as surrogates to study the fate and transport of non-fluorescent nanoparticles is limited due to high cost, detection of limit issues, and lack of sufficient data related to health effects. Systematic studies on the impact of QDs on environment and health may facilitate its safe use for environmental applications. This review summarizes the studies conducted with QDs with a focus on environmental applications and provides toxicity data important to human health.     

Chiral separation strategy in polar organic solvent chromatography and performance comparison with normal-phase liquid and supercritical-fluid chromatography

A strategy, including a rapid screening and several optimisation steps, for the separation of chiral molecules of pharmaceutical interest by polar organic solvent chromatography (POSC), using four polysaccharide-based stationary phases, is proposed and compared with previously reported strategies in normal-phase (NPLC) and supercritical fluid chromatography (SFC). In a first part of this paper, different examples demonstrate the effectiveness of the POSC strategy for fast method development. Optimisation is based on the use of experimental design to map the experimental domain in an efficient way. In the second part, the best screening results, obtained after performance of earlier defined chromatographic screening strategies in NPLC and SFC, are compared to those obtained in POSC. The three techniques show complementary separation results and allowed baseline separation of 23 of 25 compounds. POSC is found to be a very interesting separation mode compared to NPLC, because of the many fast (< 10 min) baseline separations obtained.     

Crossed characterisation of polymer-layered silicate (PLS) nanocomposite morphology: TEM, X-ray diffraction, rheology and solid-state nuclear magnetic resonance measurements

As the nanocomposite properties dramatically depend on the dispersion state of the filler in the matrix, it is essential to develop technical methods to characterise the nanodispersion both qualitatively and quantitatively. In this study, complete characterisations of the nanodispersion of organomodified clays in polyamide 6, polypropylene and poly(butylene terephtalate) are presented and discussed using different analytical tools. All four characterisation methods have been evaluated experimentally. TEM has been used to qualitatively characterise the dispersion. As TEM picture might be not fully representative of the whole sample, many pictures have to be analysed to mirror the global repartition. XRD is particularly adapted to the study of intercalated morphology of nanocomposite since the distance between two platelets can be calculated but needs TEM to provide more complete conclusions. Melt rheology and solid-state NMR are bulk analyses. During the measurement the sample is representative of the material. Rheology is relatively simple to make measurements and to get semi-quantitative data. In connection with NMR, we can get quantitative measurements on the degree of nanodispersion in the nanocomposite.     

Screening and confirmation methods for GHB determination in biological fluids

The purpose of this review is to provide a comprehensive overview of reported methods for screening and confirmation of the low-molecular-weight compound and drug of abuse gamma-hydroxybutyric acid (GHB) in biological fluids. The polarity of the compound, its endogenous presence, its rapid metabolism after ingestion, and its instability during storage (de novo formation and interconversion between GHB and its lactone form gamma-butyrolactone) are challenges for the analyst and for interpretation of a positive result. First, possible screening procedures for GHB are discussed, including colorimetric, enzymatic, and chromatography-based procedures. Confirmation methods for clinical and forensic cases mostly involve gas chromatography (coupled to mass spectrometry), although liquid chromatography and capillary zone electrophoresis have also been used. Before injection, sample-preparation techniques include (a combination of) liquid–liquid, solid-phase, or headspace extraction, and chemical modification of the polar compound. Also simple “dilute-and-shoot” may be sufficient for urine or serum. Advantages, limitations, and trends are discussed.     

Hydrophobic waterborne coating for cellulose containing hybrid organic nanoparticle pigments with vegetable oils

Vegetable oils were combined with recent nanotechnology as a sustainable method for tuning the hydrophobicity of cellulose and paper surfaces. Different soy-, sunflower-, corn-, castor-, rapeseed- and hydrogenated oils were incorporated into an aqueous dispersion of hybrid styrene maleimide nanoparticles. Here, we investigate the formation of novel coatings from these dispersions and their performance on paper and paperboard, compared with model aluminum substrates. The coated papers are evaluated by static and dynamic contact angles, microscopy, atomic force microscopy, infrared and Raman spectroscopy. The nanoparticle pigments form a porous coating after drying, while the water repellence and hydrophobicity of paperboard and paper improved with contact angles of 90–99° after drying and 98–112° after ageing. The coatings with poly(unsaturated) oils have best hydrophobicity for dispersions with an optimum viscosity of 115–150 cp required for good coverage of the paper. While homogeneous coverage of the cellulose fibers is a primary requirement, thin coatings often provide higher contact angles on paper due to roughness of the underlaying fibrous surface. After ageing, the coatings are chemically stable without oil leakage and constant imide content, while an increase in contact angles is attributed to variations in coating morphology through local re-arrangements over the paper substrate.     

Carbon monoxide adsorption on silver doped gold clusters

Well controlled gas phase experiments of the size and dopant dependent reactivity of gold clusters can shed light on the surprising discovery that nanometer sized gold particles are catalytically active. Most studies that investigate the reactivity of gold clusters in the gas phase focused on charged, small sized clusters. Here, reactivity measurements in a low-pressure reaction cell were performed to investigate carbon monoxide adsorption on neutral bare and silver doped gold clusters (Au(n)Ag(m); n = 10-45; m = 0, 1, 2) at 140 K. The size dependence of the reaction probabilities reflects the role of the electronic shells for the carbon monoxide adsorption, with closed electronic shell systems being the most reactive. In addition, the cluster's reaction probability is reduced upon substitution of gold atoms for silver. Inclusion of a single silver atom causes significant changes in the reactivity only for a few cluster sizes, whereas there is a more general reduction in the reactivity with two silver atoms in the cluster. The experimental observations are qualitatively explained on the basis of a Blyholder model, which includes dopant induced features such as electron transfer from silver to gold, reduced s-d hybrization, and changes in the cluster geometry.