Protecting biodegradable coatings releasing antimicrobial agents

This article describes the synthesis and in vitro analysis of poly(ester anhydride) antimicrobial protection coatings. Poly(ester anhydride)s composed of ricinoleic acid, sebacic acid, terephthalic acid, and isophthalic acid were used in this study. The polymers were compatible with various fillers commonly used in paint preparation. The in vitro experiments showed that the polymers are able to release diuron, an antimicrobial agent, for months. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Stereoisomers composition of 4-[(1′-methylpropyl)-oxycarbonyl]-2-oxetanone and related compounds,as precursors of fuctional polyesters,determined by chiral gas chromatography

Summary The configurational analysis of racemic and optically active stereoisomers of 4-[(1-methylpropyl)oxycarbonyl]-2-oxetanone has been carried out by using chiral gas chromatography. This technique has been successful in the stereoisomers composition determination of these -substituted -lactones prepared by two different routes and used as monomers in the preparation of malic acid stereocopolymers. Result are in good agreement with those obtained from high resolution ¹H NMR, in the presence of an Europium salt, as chiral shift reagent. This method has been extended to 3-methyl-4-[(1,2,2-trimethyl propyl)oxycarbonyl]-2-oxetanone. The exact knowledge of precursors configurational structure is very important in regard to the obtention of the corresponding polystereoisomers with a strictly controlled enantiomeric or diastereoisomeric composition and consequently with predictable properties.     

Hierarchically structured transparent hybrid membranes by in situ growth of mesostructured organosilica in host polymer

The elaborate performances characterizing natural materials result from functional hierarchical constructions at scales ranging from nanometres to millimetres, each construction allowing the material to fit the physical or chemical demands occurring at these different levels. Hierarchically structured materials start to demonstrate a high input in numerous promising applied domains such as sensors, catalysis, optics, fuel cells, smart biologic and cosmetic vectors. In particular, hierarchical hybrid materials permit the accommodation of a maximum of elementary functions in a small volume, thereby optimizing complementary possibilities and properties between inorganic and organic components. The reported strategies combine sol-gel chemistry, self-assembly routes using templates that tune the material's architecture and texture with the use of larger inorganic, organic or biological templates such as latex, organogelator-derived fibres, nanolithographic techniques or controlled phase separation. We propose an approach to forming transparent hierarchical hybrid functionalized membranes using in situ generation of mesostructured hybrid phases inside a non-porogenic hydrophobic polymeric host matrix. We demonstrate that the control of the multiple affinities existing between organic and inorganic components allows us to design the length-scale partitioning of hybrid nanomaterials with tuned functionalities and desirable size organization from ?ngstr?m to centimetre. After functionalization of the mesoporous hybrid silica component, the resulting membranes have good ionic conductivity offering interesting perspectives for the design of solid electrolytes, fuel cells and other ion-transport microdevices.     

On the study of catalytic membrane reactor for water detritiation: Membrane characterization

Tritium waste recycling is a real economic and ecological issue. Generally under the non-valuable Q₂O form (Q = H, D or T), waste can be converted into fuel Q₂ for a fusion machine (e.g. JET, ITER) by isotope exchange reaction Q₂O + H₂ = H₂O + Q₂. Such a reaction is carried out over Ni-based catalyst bed packed in a thin wall hydrogen permselective membrane tube. This catalytic membrane reactor can achieve higher conversion ratios than conventional fixed bed reactors by selective removal of reaction product Q₂ by the membrane according to Le Chatelier's Law.This paper presents some preliminary permeation tests performed on a catalytic membrane reactor. Permeabilities of pure hydrogen and deuterium as well as those of binary mixtures of hydrogen, deuterium and nitrogen have been estimated by measuring permeation fluxes at temperatures ranging from 573 to 673 K, and pressure differences up to 1.5 bar. Pure component global fluxes were linked to permeation coefficient by means of Sieverts’ law. The thin membrane (150 μm), made of Pd–Ag alloy (23 wt.%_Ag), showed good permeability and infinite selectivity toward protium and deuterium. Lower permeability values were obtained with mixtures containing non permeable gases highlighting the existence of gas phase resistance. The sensitivity of this concentration polarization phenomenon to the composition and the flow rate of the inlet was evaluated and fitted by a two-dimensional model.     

The effects of laser energy density and particle size in the selective laser sintering of polycaprolactone/progesterone specimens: morphology and drug release

The goals of this work were to fabricate specimens of different powder particle sizes and laser energy density of polycaprolactone and progesterone by selective laser sintering and evaluate the morphology by scanning electron microscopy and the mechanism of drug release in vitro. The results showed that the specimens maintained morphological uniformity, coalescence of particles, and interconnected pores distributed in the sintered structure. The drug release mechanism of all specimens studied followed a zero-order kinetics, and drug release rates were dependent on sintering degree and, consequently, on matrix erosion.     

Synergistic effects in binary systems of lubricant additives: a chemical hardness approach

Tribochemical interactions between antiwear zinc dithiophosphate (Zndtp), friction modifier molybdenum dithiocarbamate (Modtc) and detergent overbased calcium borate (CB) lubricant additives have been investigated by coupling analytical TEM and micro‐spot XPS in the tribotester Optimol of SRV GmbH (mild wear conditions in boundary lubrication). Synergistic effects have been observed on both friction and wear data, especially in the Modtc/Zndtp combination. Results have been interpreted on the basis of a chemical hardness concept: the hard and soft acids and bases (HSAB) principle, stabilisation of hard–hard pairs and the maximum hardness principle. The performance of the Modtc/Zndtp mixture is mainly due to the generation of MoS₂ single sheets and the digestion of MoO₃, which is also formed, by the zinc polyphosphate glass. The final result of the tribochemical reaction is a tribofilm composed of MoS₂ sheets embedded in a mixed Mo/Zn polyphosphate glass. The CB/Modtc mixture has a similar mechanism except that the oxide is not completely eliminated, due to the softer borate anion compared with the phosphate one. This revised version was published online in July 2006 with corrections to the Cover Date.     

New method based on capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) to monitor interaction between nanoparticles and the amyloid-β peptide

A novel application of capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was proposed to efficiently detect and monitor the interaction between polymeric nanoparticles and the β-Amyloid peptide (Aβ(1-42)), a biomarker for Alzheimer's Disease (AD), at concentrations close to physiological conditions. The CE-LIF method allowed the interaction between PEGylated poly(alkyl cyanoacrylate) nanoparticles (NPs) and the soluble Aβ(1-42) peptide monomers to be highlighted. These results were confirmed by surface plasmon resonance (SPR) and confocal laser scanning microscopy (CLSM). Whereas SPR showed an interaction between the NPs and the Aβ(1-42) peptide, CLSM allowed the formation of large aggregates/assemblies at high NP and peptide concentrations to be visualized. All these results suggested that these nanoparticles could bind the Aβ(1-42) peptide and influence its aggregation kinetics. Interestingly, the non-PEGylated poly(alkyl cyanoacrylate) NPs did not alter the aggregation kinetics of the Aβ(1-42) peptide, thus emphasizing the high level of discrimination of the CE-LIF method with respect to NPs.     

Mo6 cluster-based compounds for energy conversion applications: comparative study of photoluminescence and cathodoluminescence

Abstract

We report the photoluminescence (PL) and cathodoluminescence (CL) properties of face-capped [Mo₆Xⁱ₈L^a₆]^2? (X = Cl, Br, I; L = organic or inorganic ligands) cluster units. We show that the emission of Mo₆ metal atom clusters depends not only on the nature of X and L ligands bound to the cluster and counter-cations, but also on the excitation source. Seven members of the A_xMo₆Xⁱ₈L^a₆ series (A = Cs⁺, (n-C₄H₉)₄N⁺, NH₄⁺) were selected to evaluate the influence of counter-cations and ligands on de-excitation mechanisms responsible for multicomponent emission of cluster units. This study evaluates the ageing of each member of the series, which is crucial for further energy conversion applications (photovoltaic, lighting, water splitting, etc.).