Cobalt tris(4-vinylphenyl)corrole: out of the frying pan into the polymer.

A novel cobalt corrole bearing 4-vinylphenyl groups at the 5,10,15-meso-positions of the macrocycle has been synthesized from tris(4-bromophenyl)corrole using a Suzuki coupling reaction. The spectral and electrochemical properties are reported in CH2Cl2 along with its ability to form a highly stable six-coordinate complex and cross-linked corrole-based polymer in a 59% yield.

Olive mill wastewater from a liquid biological waste to a carbon/oxocalcium composite for selective and efficient removal of methylene blue and paracetamol from aqueous solution.

In this study, a Carbon/Oxocalcium was prepared from olive mill wastewater and successfully applied to the removal of paracetamol and methylene blue (MB) from an aqueous medium. The optimized composite (0.3 % CaO) is rich in anionic sites, porous and has a specific surface area of about 1383 m2.g-1. Adsorption tests showed significant adsorption capacities up to 1141 mg.g-1. The adsorption of MB and paracetamol is well described by the Redlich-Peterson and Dubinin-Radushkevich isotherm, respectively. Moreover, the adsorption kinetics fitted to pseudo-second order. The π -π interactions, hydrogen bonds and electrostatic interactions were responsible for the adsorption of paracetamol and MB substrates. This work develops by a single, easy and simple action a new effective and selective material for the removal of emerging pollutants, a new method for the development of more stable carbon composites and a cost-effective method for the valorization of olive mill wastewater.

Pebax-Based Composite Membranes with High Transport Properties Enhanced by ZIF-8 for CO2 Separation.

A series of mixed matrix membranes containing poly (ether-block-amide) Pebax 1657 as matrix and polyethylene glycol (PEG) and Zeolitic Imidazolate Framework-8 (ZIF-8) as additives, were prepared and tested for CO2 separation. The membranes were prepared by solvent evaporation method and were characterized by TGA, DSC, SEM, and gas permeation measurements. The effects of PEG and its molecular weight, and the percentage of ZIF-8 into Pebax matrix were investigated. The results showed that the addition of PEG to Pebax/ZIF-8 blends avoid the agglomeration of ZIF-8 particles. A synergic effect between PEG and ZIF was particularly observed for high ZIF-8 content, because the initial permeability of pristine Pebax was multiplied by three (from 54 to 161 Barrers) while keeping the CO2 selectivity (αCO2/N2 = 61, αCO2/CH4 = 12 and αCO2/O2 = 23). Finally, the mechanism of CO2 transport is essentially governed by the solubility of CO2 into the membranes. Therefore, this new Pebax/PEG/ZIF-8 system seems to be a promising approach to develop new selective membranes for CO2 with high permeability.

Structural and Barrier Properties of Compatibilized PE/PA6 Multinanolayer Films.

The barrier performance and structural lightening of organic materials are increasingly desired and constitute a major challenge for manufacturers, particularly for transport and packaging. A promising technique which tends to emerge in recent years is that of multinanolayer coextrusion. The advantage is that it can produce multilayers made of thousands of very thin layers, leading to new properties due to crystalline morphology changes induced by confinement. This paper is focusing on the study of multinanolayered films with alternated polyethylene (PE), compatibilizer (PEgMA) and polyamide 6 (PA6) layers and made by a forced assembly coextrusion process equipped with layer multiplying elements (LME). PE/PA6 multilayer films consisting of 5 to 2049 layers (respectively 0 to 9 LME) were successfully obtained with well-organized multilayered structure. The evolution of the morphology and the microstructure of these two semi-crystalline polymers, when the thickness of each polymer layer decreases from micro-scale to nano-scale, was correlated to the water and gas transport properties of the PE/PA multilayers. The expected improvement of barrier properties was limited due to the on-edge orientation of crystals in very thin PE and PA6 layers. Despite this change of crystalline morphology, a slight improvement of the gas barrier properties was shown by comparing experimental results with permeabilities predicted on the basis of a serial model developed by considering a PE/PA6 interphase. This interphase observed by TEM images and the on-edge crystal orientation in multilayers were evidenced from mechanical properties showing an increase of the stiffness and the strength.

Polysaccharide-based chromatographic adsorbents for virus purification and viral clearance.

Viruses still pose a significant threat to human and animal health worldwide. In the fight against viral infections, high-purity viral stocks are needed for manufacture of safer vaccines. It is also a priority to ensure the viral safety of biopharmaceuticals such as blood products. Chromatography techniques are widely implemented at both academic and industrial levels in the purification of viral particles, whole viruses and virus-like particles to remove viral contaminants from biopharmaceutical products. This paper focuses on polysaccharide adsorbents, particulate resins and membrane adsorbers, used in virus purification/removal chromatography processes. Different chromatographic modes are surveyed, with particular attention to ion exchange and affinity/pseudo-affinity adsorbents among which commercially available agarose-based resins (Sepharose®) and cellulose-based membrane adsorbers (Sartobind®) occupy a dominant position. Mainly built on the development of new ligands coupled to conventional agarose/cellulose matrices, the development perspectives of polysaccharide-based chromatography media in this antiviral area are stressed in the conclusive part.

Polysaccharide-based chromatographic adsorbents for virus purification and viral clearance / 药物分析学报

Viruses still pose a significant threat to human and animal health worldwide. In the fight against viral infections, high-purity viral stocks are needed for manufacture of safer vaccines. It is also a priority to ensure the viral safety of biopharmaceuticals such as blood products. Chromatography techniques are widely implemented at both academic and industrial levels in the purification of viral particles, whole viruses and virus-like particles to remove viral contaminants from biopharmaceutical products. This paper focuses on polysaccharide adsorbents, particulate resins and membrane adsorbers, used in virus purification/removal chromatography processes. Different chromatographic modes are surveyed, with particular attention to ion exchange and affinity/pseudo-affinity adsorbents among which commercially available agarose-based resins (Sepharose?) and cellulose-based membrane adsorbers (Sartobind?) occupy a dominant position. Mainly built on the development of new ligands coupled to conventional agarose/cellulose matrices, the development perspectives of polysaccharide-based chromatography media in this antiviral area are stressed in the conclusive part.

Cellulose-based virus-retentive filters: a review.

Viral filtration is a critical step in the purification of biologics and in the monitoring of microbiological water quality. Viral filters are also essential protection elements against airborne viral particles. The present review first focuses on cellulose-based filter media currently used for size-exclusion and/or adsorptive filtration of viruses from biopharmaceutical and environmental water samples. Data from spiking studies quantifying the viral filtration performance of cellulosic filters are detailed, i.e., first, the virus reduction capacity of regenerated cellulose hollow fiber filters in the manufacturing process of blood products and, second, the efficiency of virus recovery/concentration from water samples by the viradel (virus adsorption-elution) method using charge modified, electropositive cellulosic filters or conventional electronegative cellulose ester microfilters. Viral analysis of field water samples by the viradel technique is also surveyed. This review then describes cellulose-based filter media used in individual protection equipment against airborne viral pathogens, presenting innovative filtration media with virucidal properties. Some pros and cons of cellulosic viral filters and perspectives for cellulose-based materials in viral filtration are underlined in the review.

Polysaccharide-based antibiofilm surfaces.

Surface treatment by natural or modified polysaccharide polymers is a promising means to fight against implant-associated biofilm infections. The present review focuses on polysaccharide-based coatings that have been proposed over the last ten years to impede biofilm formation on material surfaces exposed to bacterial contamination. Anti-adhesive and bactericidal coatings are considered. Besides classical hydrophilic coatings based on hyaluronic acid and heparin, the promising anti-adhesive properties of the algal polysaccharide ulvan are underlined. Surface functionalization by antimicrobial chitosan and derivatives is extensively surveyed, in particular chitosan association with other polysaccharides in layer-by-layer assemblies to form both anti-adhesive and bactericidal coatings. STATEMENT OF SIGNIFICANCE: Bacterial contamination of surfaces, leading to biofilm formation, is a major problem in fields as diverse as medicine, first, but also food and cosmetics. Many prophylactic strategies have emerged to try to eliminate or reduce bacterial adhesion and biofilm formation on surfaces of materials exposed to bacterial contamination, in particular implant materials. Polysaccharides are widely distributed in nature. A number of these natural polymers display antibiofilm properties. Hence, surface treatment by natural or modified polysaccharides is a promising means to fight against implant-associated biofilm infections. The present manuscript is an in-depth look at polysaccharide-based antibiofilm surfaces that have been proposed over the last ten years. This review, which is a novelty compared to published literature, will bring well documented and updated information to readers of Acta Biomaterialia.

Antiviral effects of polyphenols: development of bio-based cleaning wipes and filters.

Polyphenol molecules play multiple essential roles in plant physiology such as defences against plant-pathogens and micro-organisms. The present study reports a chemical modification of the surface of non-woven cellulosic fibre filters (Kimwipes(®)) by fixing polyphenol in order to confer them antiviral properties. The grafting of the non-woven fibres by the antiviral entity was performed using laccase. T4D bacteriophage virus of Escherichia coli B was used as virus model. Catechin polyphenol was tested as antiviral entity. Proteomic experiments were performed to quantify the potential protein target of catechin on viruses. When the modified filter was in contact with the viral suspension a large improvement in the reduction of the viral concentration was observed (5-log after 1h). Thus, we propose that this material could be used as virucidal wipes for the virus elimination from contaminated surfaces. Virus filtration experiments were performed by spraying an aerial suspension of T4D bacteriophage virus through the designed filter. The best virus capture factor f (ratio of upstream to downstream virus contents) was obtained when using 2 functionalized filters (f=2.9×10(3)). When these 2 layers were placed inside a commercial medical mask in place of its cellulose layer (Kolmi M24001 mask) (f=3.5×10(4)), the f ratio then reached 2.6×10(5) for 2h of filtration. Based on these results, this novel bio-based antiviral mask represents a significant improvement over conventional medical masks.

Role of molecular properties of ulvans on their ability to elaborate antiadhesive surfaces.

Antiadhesive properties of polysaccharides (such ulvans) once immobilized on a surface are described in the literature but the parameters governing their antifouling properties are not yet well identified. In the present study, the relationship between molecular parameters of ulvans and the inhibition of bacterial adhesion was investigated. To this aim, various ulvans were grafted on silicon wafers under two different experimental immobilization conditions. Results showed that the experimental immobilization conditions and the polysaccharides molecular weight led to specific layer conformations which exhibited a key role in the surface antiadhesive properties.

Antiadhesive activity of ulvan polysaccharides covalently immobilized onto titanium surface.

Bacterial adhesion leading to biofilm formation on the surface of implants is responsible for pathogenesis infections. One promising strategy to reduce the risk of infection consists of modifying implant surfaces by antibacterial coating. In the present study, the ability of ulvan, a non biocidal algal polysaccharide, to limit bacterial adhesion on titanium was investigated. To this end, titanium surfaces were modified by two different ulvans. Polysaccharides were covalently immobilized on titanium surfaces which had been previously functionalized by self assembled monolayers of aminoundecyltrimethoxysilane (AUTMS). Each step in the modification process was characterized by contact angle, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Bacterial adhesion assays showed that immobilized ulvans on titanium surface strongly decreased by about 90% the adhesion of Pseudomonas aeruginosa. Moreover, AFM observations showed that the polysaccharide also inhibited the bacterial spreading on the surface but not cell-to-cell interaction. The permanence of the anti-adhesive effect of the surfaces was finally tested on a non-motile organism, i.e., Staphylococcus epidermidis. The results showed that the effect was maintained for at least 24h.

Polysaccharide hydrolases are released with mucilages after water hydration of flax seeds.

Water imbibition of flax seed induces secretion of mucilages whose physico-chemical properties vary according to genotype and environment. The viscosity and composition of mucilage have ecological implications and also affect the utility of the crop. Several types of enzymes are secreted along with the mucilage. Our objective was to study these enzymes in the context of the composition and physical properties of the mucilage. The kinetics of production by flax seeds (variety Eden) of i) mucilages, ii) glycosidases and iii) endo-hydrolases were followed over 48 h under sterile conditions. The impact of enzymatic activities on mucilage was investigated by SEC-MALLS, viscosimetry and sugar composition. The mucilages consisted mainly of rhamnogalacturonan-I (RG-I, 52-62%) and arabinoxylan (AX, 27-36%). RG-I related enzyme activities (rhamnogalacturonase and ß,d-galactosidase) were quantified, together with AX related activity of α,l-arabinofuranosidase, ß,d-xylosidase and ß-xylanase. Maximal xylanase activity was reached after 4 h seed-hydration, when the minimal viscosity of the polysaccharides was observed, and the AX/RG-I ratio was the lowest. At that time, poly and oligosaccharides mainly contained pectic sugars. From 24 to 48 h water-hydration, when mucilages more tightly associated with cell walls were released, the glycosidase activities per g mucilage became maximal; the percentage, average molar-mass and viscosity of the polysaccharides decreased. Glucose, xylose and arabinose were the main sugars in the oligomer fraction. Our data confirmed the presence of ß-d xylosidase and α-l-arabinofuranosidase activities and provided evidence for significant pectinase activities in flax mucilages. They also indicate an impact of enzymatic activities on the physicochemical properties of mucilages.

Investigation of electrostrictive polymer efficiency for mechanical energy harvesting.

The purpose of this paper is to propose new means for harvesting energy using electrostrictive polymers. Recent trends in energy conversion mechanisms have demonstrated the abilities of electrostrictive polymers for converting mechanical vibrations into electricity. In particular, such materials present advantageous features such as a high productivity, high flexibility, and ease of processing; hence, the application of these materials for energy harvesting purposes has been of significant interest over the last few years. This paper discusses the development of a model that is able to predict the energy harvesting capabilities of an electrostrictive polymer. Moreover, the energy scavenging abilities of an electrostrictive composite composed of terpolymer poly(vinylidenefluoride-trofluoroethylene- chlorofluoroethylene) [P(VDF-TrFE-CFE)] filled with 1 vol% carbon black (C) is evaluated. Experimental measurements of the harvested power and current have been compared with the theoretical behavior predicted by the proposed model. A good agreement was observed between the two sets of data, which consequently validated the proposed modeling to optimize the choice of materials. It was also shown that the incorporation of nanofillers in P(VDF-TrFE-CFE) increased the harvested power.

Analysis of ac-dc conversion for energy harvesting using an electrostrictive polymer P(VDF-TrFE-CFE).

Harvesting systems capable of transforming unused environmental energy into useful electrical energy have been extensively studied for the last two decades. The recent development of electrostrictive polymers has generated new opportunities for harvesting energy. The contribution of this study lies in the design and validation of electrostrictive polymer- based harvesters able to deliver dc output voltage to the load terminal, making the practical application of such material for self-powered devices much more realistic. Theoretical analysis supported by experimental investigations showed that an energy harvesting module with ac-to-dc conversion allows scavenging power up to 7 µW using a bias electric field of 10 V/µm and a transverse strain of 0.2%. This represents a power density of 280 µW/cm(3) at 100 Hz, which is much higher than the corresponding values of most piezo-based harvesters.

Modeling and experimentation on an electrostrictive polymer composite for energy harvesting.

The harvesting of energy from ambient environments is an emerging technology with potential for numerous applications, including portable electronic devices for renewable energy. Most of the current research activities refer to classical piezoelectric ceramic materials, but more recently the development of electrostrictive polymers has generated novel opportunities for high-strain actuators. At present, the investigation of using electrostrictive polymers for energy harvesting (a conversion of mechanical to electrical energy) is beginning to show potential for this application. This paper discusses the development of a model that is able to predict the energy harvesting capabilities of an electrostrictive polymer composite (EPC). An equivalent electrical scheme has been developed by using the model of current that was recently developed by our group. After the validation of the model on a macroscopic level, an empirical relationship was established to predict the value of power from the electrostriction coefficient, the dielectric permittivity, and the compliance of the material. Finally, results indicated that the dielectric permittivity was the crucial parameter for energy harvesting.

Novel metal-complexing membrane containing poly(4-vinylpyridine) for removal of Hg(II) from aqueous solution.

A novel poly(vinyl alcohol)/poly(4-vinylpyridine) (PVA/P(4)VP) complexing membrane for removal of Hg(II) ions from aqueous solutions represents a significant improvement over a previously reported PVA/poly(ethylenimine) (PEI) membrane. This membrane was prepared by the semi-interpenetrating polymer network technique, and its cross-linking by three different agents was studied. The best results were obtained with gaseous 1,2-dibromoethane at 140 degrees C for 1 h that gave a membrane with a swelling ratio of 0.66. The sorption reaction of Hg(II) followed a first-order rate law, and the rate-limiting step was shown to be the association of Hg(II) ions with the complexing sites of P(4)VP. Sorption experiments at pH 2.5 showed that the retention ratio could reach 100% under optimized conditions for the initial concentration of Hg(II) and mass of membrane, c(0) = 100 mg L(-1) and m(D) = 100 mg, respectively. The retention ratio was remarkably insensitive to water hardness or the presence of NaCl, suggesting possible use for the purification of real wastewaters. The retention capacity of the membrane was 450 mg g(-1) compared to 311 mg g(-1) reported for the PVA/PEI membrane. Sorption isotherms were determined at various temperatures, according to the Langmuir model, for the determination of the thermodynamical parameters. When T increased, mercury uptake at equilibrium did not change, whereas the sorption coefficient b decreased and the change in free energy DeltaG degrees decreased. This result is probably due to a large favorable entropic effect, ascribed to the displacement of protons from the protonated sites of P(4)VP while they bind with Hg(II) ions. The membrane could be regenerated by 0.5 M nitric acid with less than 3% loss of efficiency. The membrane was used for filtration experiments. The elimination ratio was 99.9% or more for filtration of Hg(II) solutions in the c(0) = 16.6-89.1 mg L(-1) range.

Single crystals and nonlinear process for outstanding vibration-powered electrical generators.

This paper compares the performances of vibration-powered electrical generators using a piezoelectric ceramic and a piezoelectric single crystal associated to several power conditioning circuits. A new approach of the piezoelectric power conversion based on a nonlinear voltage processing is presented, leading to three novel high performance power conditioning interfaces. Theoretical predictions and experimental results show that the nonlinear processing technique may increase the power harvested by a factor of 8 compared to standard techniques. Moreover, it is shown that, for a given energy harvesting technique, generators using single crystals deliver 20 times more power than generators using piezoelectric ceramics.

Modeling of elastic nonlinearities in ferroelectric materials including nonlinear losses: application to nonlinear resonance mode of relaxors single crystals.

(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) and (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) single crystals are considered to behave like soft Pb(Zr,Ti)O3 (PZT) ceramics because of their small mechanical quality factor Qm and poor stability under external disturbances (Qm > 500-1000 for hard PZT ceramic, and Qm < 100 for soft PZT and PMN-PT and PZN-PT single crystals). At weak signal excitation of the first resonance mode, the displacement at the end of a lateral bar is proportional to the Q31d31 figure of merit that is very close to that found for hard PZT. Indeed the very large piezoelectric coefficient compensates the low Qm. But increasing alternating current (AC) field results in the appearance of strong non-linearities through a shift of the resonance frequency and jumps phenomenon observed on increasing and decreasing frequency sweep. It is shown in this paper that these nonlinearities are due to the nonlinear elastic compliance that can be modeled by a third order development of the constitutive piezoelectric equations. Experiments on PMN-PT and PZN-PT single crystals are used for comparison with the model to show the viability of the approach. Both the frequency shift and jumps phenomenon are simulated with a very good agreement with experimental results. The importance is also shown of losses associated with the third order term responsible for the large decrease of the mechanical quality factor for high strain levels. Thus, the nonlinear losses are related to the hysteresis of domain wall motion when subjected to large displacements.

Stability of morphotropic (110) oriented 0.65PMN-0.35PT single crystals.

Electromechanical properties of (1-x)Pb (Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystals with x = 0.35 were investigated as a function of different external disturbances. The polarization dependence on the electromechanical properties was first studied in order to determine the best polarization path. The correlation with X-ray measured phase ratio is presented and shows that the maximum of electromechanical properties may be correlated with a minimum rhombohedral/tetragonal phase ratio. Temperature, stress, electric field, and time (aging) stability was studied in order to determine performance-limiting factors of these materials. The rhombohedral/tetragonal phase transition is observed on temperature (80 degrees C), inducing a decrease of the electromechanical coupling factor (from 85% to 50%); but the whole properties are recovered while returning to room temperature. Stress measurement shows a large depoling of sample for stresses above 30 MPa. The PMN-PT single crystals were found to be surprisingly stable during aging, except for mechanical and dielectric losses. The same tendency was found on alternating current (AC) electric field dependence.