Singling Out the Role of Molecular Weight in the Crystallization Kinetics of Polyester/Clay Bionanocomposites Obtained by In Situ Step Growth Polycondensation

The isothermal crystallization kinetics of a set of bio-nanocomposites produced by in situ catalytic step growth polycondensation of adipic acid and 1,4-butanediol in the presence of Moroccan clay beidellite (BDT) organo-modified with hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide, CTA) was investigated and compared with that of the parent poly(butylene adipate) (PBA) matrices from which the clay had been extracted. In situ bio-nanocomposites had different contents (0−5 wt %) of CTA/BDT nanofillers characterized by different extents of organo-modification (CTA/BDT equivalent ratios from 0 to 5). Theb isothermal crystallization rates of the ionanocomposites and of the parent PBA matrices were investigated by differential scanning calorimetry (DSC) at 45, 40, and 37 °C and analyzed according to the Avrami model. The bionanocomposites with an intermediate (2 wt %) concentration of organoclays with a higher CTA/BDT ratio (3 and 5) showed the highest exfoliation degree, along with an increase in the crystallization rates, compared to those of the parent PBA matrices, which was larger than that in the other nanocomposites. The lack of a simple correlation between the nanoclay content/composition and crystallization kinetics was ascribed to the molecular mass, an additional variable for in situ bio-nanocomposites as compared to nanocomposites prepared by simple physical blending of nanoclays with a single polymer matrix. The specific contribution of the molecular mass to the crystallization kinetics was untangled from those of the organoclay content and CTA/BDT ratio by comparing each bio-nanocomposite with its parent polymer matrix. The crystallization rate of the nanocomposites was always found to reach a maximum within an intermediate range of molecular weights of the polymer matrix, a behavior previously reported only for pure polymers. Such differences in the crystallization rate of in situ bio-nanocomposites may affect the crystalline phase morphology and, in polymorphs such as in PBA, phase composition, with consequent effects on properties that may be of interest for specific applications

Pd embedded in chitosan microspheres as tunable soft-materials for Sonogashira cross-coupling in water-ethanol mixture

Easy shaping of chitosan (CS) as porous self-standing nanofibrillar microspheres allows their use as a palladium carrier. Amino-groups on CS enable the modulation of Pd coordination, giving rise to three different support-catalyst interactions: weakly-coordinated Pd-CS in native CS, incarcerated Pd-CS-Glu in cross-linked CS and strongly-ligated Pd-CS-SH, obtained by the introduction of thiol arms in CS. These catalysts efficiently promote Sonogashira cross-coupling of a large library of functional substrates under mild and sustainable conditions (water-ethanol as solvent at 65 degrees C) and stand as recyclable, metal-scavenging catalytic systems.Frindy, S.; Primo Arnau, AM.; Lahcini, M.; Bousmina, M.; García Gómez, H.; El Kadib, A. (2015). Pd embedded in chitosan microspheres as tunable soft-materials for Sonogashira cross-coupling in water-ethanol mixture. Green Chemistry. 17(3):1893-1898. doi:10.1039/c4gc02175dS18931898173Johansson Seechurn, C. C. C., Kitching, M. O., Colacot, T. J., & Snieckus, V. (2012). Palladium-Catalyzed Cross-Coupling: A Historical Contextual Perspective to the 2010 Nobel Prize. Angewandte Chemie International Edition, 51(21), 5062-5085. doi:10.1002/anie.201107017Sehnal, P., Taylor, R. J. K., & Fairlamb, I. J. S. (2010). Emergence of Palladium(IV) Chemistry in Synthesis and Catalysis. Chemical Reviews, 110(2), 824-889. doi:10.1021/cr9003242Torborg, C., & Beller, M. (2009). Recent Applications of Palladium-Catalyzed Coupling Reactions in the Pharmaceutical, Agrochemical, and Fine Chemical Industries. Advanced Synthesis & Catalysis, 351(18), 3027-3043. doi:10.1002/adsc.200900587Hartwig, J. F. (2008). Carbon–heteroatom bond formation catalysed by organometallic complexes. Nature, 455(7211), 314-322. doi:10.1038/nature07369Loska, R., Volla, C. M. R., & Vogel, P. (2008). Iron-Catalyzed Mizoroki-Heck Cross-Coupling Reaction with Styrenes. Advanced Synthesis & Catalysis, 350(18), 2859-2864. doi:10.1002/adsc.200800662Sun, C.-L., Li, B.-J., & Shi, Z.-J. (2011). Direct C−H Transformation via Iron Catalysis. Chemical Reviews, 111(3), 1293-1314. doi:10.1021/cr100198wCzaplik, W. M., Mayer, M., Cvengroš, J., & von Wangelin, A. J. (2009). Coming of Age: Sustainable Iron-Catalyzed Cross-Coupling Reactions. ChemSusChem, 2(5), 396-417. doi:10.1002/cssc.200900055Fürstner, A., Leitner, A., Méndez, M., & Krause, H. (2002). Iron-Catalyzed Cross-Coupling Reactions. Journal of the American Chemical Society, 124(46), 13856-13863. doi:10.1021/ja027190tBarluenga, J., & Valdés, C. (2011). Tosylhydrazones: New Uses for Classic Reagents in Palladium-Catalyzed Cross-Coupling and Metal-Free Reactions. Angewandte Chemie International Edition, 50(33), 7486-7500. doi:10.1002/anie.201007961Yin, & Liebscher, J. (2007). Carbon−Carbon Coupling Reactions Catalyzed by Heterogeneous Palladium Catalysts. Chemical Reviews, 107(1), 133-173. doi:10.1021/cr0505674Phan, N. T. S., Van Der Sluys, M., & Jones, C. W. (2006). On the Nature of the Active Species in Palladium Catalyzed Mizoroki–Heck and Suzuki–Miyaura Couplings – Homogeneous or Heterogeneous Catalysis, A Critical Review. Advanced Synthesis & Catalysis, 348(6), 609-679. doi:10.1002/adsc.200505473Weck, M., & Jones, C. W. (2007). Mizoroki−Heck Coupling Using Immobilized Molecular Precatalysts:  Leaching Active Species from Pd Pincers, Entrapped Pd Salts, and Pd NHC Complexes. Inorganic Chemistry, 46(6), 1865-1875. doi:10.1021/ic061898hWEBB, J., MACQUARRIE, S., MCELENEY, K., & CRUDDEN, C. (2007). Mesoporous silica-supported Pd catalysts: An investigation into structure, activity, leaching and heterogeneity. Journal of Catalysis, 252(1), 97-109. doi:10.1016/j.jcat.2007.09.007Garrett, C. E., & Prasad, K. (2004). The Art of Meeting Palladium Specifications in Active Pharmaceutical Ingredients Produced by Pd-Catalyzed Reactions. Advanced Synthesis & Catalysis, 346(8), 889-900. doi:10.1002/adsc.200404071Glasspoole, B. W., Webb, J. D., & Crudden, C. M. (2009). Catalysis with chemically modified mesoporous silicas: Stability of the mesostructure under Suzuki–Miyaura reaction conditions. Journal of Catalysis, 265(2), 148-154. doi:10.1016/j.jcat.2009.04.020Modak, A., Mondal, J., & Bhaumik, A. (2012). Pd-grafted periodic mesoporous organosilica: an efficient heterogeneous catalyst for Hiyama and Sonogashira couplings, and cyanation reactions. Green Chemistry, 14(10), 2840. doi:10.1039/c2gc35820dMacquarrie, D. J., & Hardy, J. J. E. (2005). Applications of Functionalized Chitosan in Catalysis†. Industrial & Engineering Chemistry Research, 44(23), 8499-8520. doi:10.1021/ie050007vA. El Kadib , ChemSusChem20158217244El Kadib, A., Primo, A., Molvinger, K., Bousmina, M., & Brunel, D. (2011). Nanosized Vanadium, Tungsten and Molybdenum Oxide Clusters Grown in Porous Chitosan Microspheres as Promising Hybrid Materials for Selective Alcohol Oxidation. Chemistry – A European Journal, 17(28), 7940-7946. doi:10.1002/chem.201003740El Kadib, A., & Bousmina, M. (2012). Chitosan Bio-Based Organic-Inorganic Hybrid Aerogel Microspheres. Chemistry - A European Journal, 18(27), 8264-8277. doi:10.1002/chem.201104006Kadib, A. E., Bousmina, M., & Brunel, D. (2014). Recent Progress in Chitosan Bio-Based Soft Nanomaterials. Journal of Nanoscience and Nanotechnology, 14(1), 308-331. doi:10.1166/jnn.2014.9012Primo, A., & Quignard, F. (2010). Chitosan as efficient porous support for dispersion of highly active gold nanoparticles: design of hybrid catalyst for carbon–carbon bond formation. Chemical Communications, 46(30), 5593. doi:10.1039/c0cc01137aValentin, R., Molvinger, K., Quignard, F., & Brunel, D. (2003). Supercritical CO2 dried chitosan: an efficient intrinsic heterogeneous catalyst in fine chemistry. New Journal of Chemistry, 27(12), 1690. doi:10.1039/b310109fPrimo, A., Atienzar, P., Sanchez, E., Delgado, J. M., & García, H. (2012). From biomass wastes to large-area, high-quality, N-doped graphene: catalyst-free carbonization of chitosan coatings on arbitrary substrates. Chemical Communications, 48(74), 9254. doi:10.1039/c2cc34978gNgah, W. S. W., Ab Ghani, S., & Kamari, A. (2005). Adsorption behaviour of Fe(II) and Fe(III) ions in aqueous solution on chitosan and cross-linked chitosan beads. Bioresource Technology, 96(4), 443-450. doi:10.1016/j.biortech.2004.05.022El Hankari, S., El Kadib, A., Finiels, A., Bouhaouss, A., Moreau, J. J. E., Crudden, C. M., … Hesemann, P. (2011). SBA-15-Type Organosilica with 4-Mercapto-N,N-bis-(3-Si-propyl)butanamide for Palladium Scavenging and Cross-Coupling Catalysis. Chemistry - A European Journal, 17(32), 8984-8994. doi:10.1002/chem.201002190Crudden, C. M., Sateesh, M., & Lewis, R. (2005). Mercaptopropyl-Modified Mesoporous Silica:  A Remarkable Support for the Preparation of a Reusable, Heterogeneous Palladium Catalyst for Coupling Reactions. Journal of the American Chemical Society, 127(28), 10045-10050. doi:10.1021/ja0430954McEleney, K., Crudden, C. M., & Horton, J. H. (2009). X-ray Photoelectron Spectroscopy and the Auger Parameter As Tools for Characterization of Silica-Supported Pd Catalysts for the Suzuki−Miyaura Reaction. The Journal of Physical Chemistry C, 113(5), 1901-1907. doi:10.1021/jp808837kRoy, A. S., Mondal, J., Banerjee, B., Mondal, P., Bhaumik, A., & Islam, S. M. (2014). Pd-grafted porous metal–organic framework material as an efficient and reusable heterogeneous catalyst for C–C coupling reactions in water. Applied Catalysis A: General, 469, 320-327. doi:10.1016/j.apcata.2013.10.017Kadib, A. E., Molvinger, K., Cacciaguerra, T., Bousmina, M., & Brunel, D. (2011). Chitosan templated synthesis of porous metal oxide microspheres with filamentary nanostructures. Microporous and Mesoporous Materials, 142(1), 301-307. doi:10.1016/j.micromeso.2010.12.012Kühbeck, D., Saidulu, G., Reddy, K. R., & Díaz, D. D. (2012). Critical assessment of the efficiency of chitosan biohydrogel beads as recyclable and heterogeneous organocatalyst for C–C bond formation. Green Chem., 14(2), 378-392. doi:10.1039/c1gc15925aKhalafi-Nezhad, A., & Mohammadi, S. (2014). Chitosan supported ionic liquid: a recyclable wet and dry catalyst for the direct conversion of aldehydes into nitriles and amides under mild conditions. RSC Advances, 4(27), 13782. doi:10.1039/c3ra43440kEl Kadib, A., McEleney, K., Seki, T., Wood, T. K., & Crudden, C. M. (2011). Cross-Coupling in the Preparation of Pharmaceutically Relevant Substrates using Palladium Supported on Functionalized Mesoporous Silicas. ChemCatChem, 3(8), 1281-1285. doi:10.1002/cctc.20110002

Insightful understanding of the role of clay topology on the stability of biomimetic hybrid chitosan-clay thin films and CO2-dried porous aerogel microspheres

[EN] Three natural clay-based microstructures, namely layered montmorillonite (MMT), nanotubular halloysite (HNT) and micro-fibrillar sepiolite (SP) were used for the synthesis of hybrid chitosan-clay thin films and porous aerogel microspheres. At a first glance, a decrease in the viscosity of the three gel forming solutions was noticed as a result of breaking the mutual polymeric chains interaction by the clay microstructure. Upon casting, chitosan-clay films displayed enhanced hydrophilicity in the order CS < CS-MMT < CS-HNT < CS-SP. Irrespective to the clay microstructure, an improvement in the mechanical properties of the chitosan-clay films has been substantiated with CS-SP reaching the highest value at 5% clay loading. While clay addition provides a way to resist the shrinkage occurring for native chitosan, the enhanced hydrophilicity associated to the water content affects the efficacy of the CO2 super-critical drying as the most hydrophilic CS-SP microspheres face the highest shrinkage, resulting in a lowest specific surface area compared to CS-HNT and CS-MMT. Chitosan-clay exhibits enhanced thermal properties with the degradation delayed in the order CS < CS-MMT < CS-HNT < CS-SP. Under acidic environment, a longevity has been substantiated for chitosan-clay compared to native chitosan, evidencing the beneficial protective effect of the clay particulates for the biopolymer. However, under hydrothermal treatment, the presence of clay was found to be detrimental to the material stability as a significant shrinkage occurs in hybrid CS-clay microspheres, which is attributed again to their increased hydrophilicity compared to the native polymeric microspheres. In this framework, a peculiar behavior was observed for CS-MMT, with the microspheres standing both against contraction during CO2 gel drying and under hydrothermal conditions. The knowledge gained from this rational design will constitute a guideline toward the preparation of ultra-stable, practically-optimized food-packaging films and commercially scalable porous bio-based adsorbents.S. F thanks MAScIR foundation, CNRST and Erasmus Mundus-Maghreb & Egypt- EMMAG.Frindy, S.; Primo Arnau, AM.; Qaiss, AEK.; Bouhfid, R.; Lahcini, M.; García Gómez, H.; Bousmina, M.... (2016). Insightful understanding of the role of clay topology on the stability of biomimetic hybrid chitosan-clay thin films and CO2-dried porous aerogel microspheres. Carbohydrate Polymers. 146:353-361. doi:10.1016/j.cabpel.2016.03.022S35336114

Highly thermostable and crystalline poly(butylene adipate) bionanocomposites prepared by in situ polycondensation with organically modified Moroccan Beidellite clay

Bionancomposites from bioplastics and nanoclays are of great interest for packaging, agricultural, and other large volume and niche applications due to their enhanced physical, thermal, mechanical, and processing characteristics compared to the parent polymer. In this study, the biodegradable polyester poly(butylene adipate) (PBA) was synthesized by in situ polycondensation catalyzed by titanium tetrabutoxide in the presence of the natural Moroccan clay Beidellite (BDT). Optimisation of the nanoclay exfoliation in the bionanocomposite was achieved by cation exchange of BDT with cetyltrimethylammonium bromide, CTA, and by selecting the most effective among a range of organically modified xCTA-BDT (x=CTA/BDT equivalent feed ratio). FT-IR, 1H NMR, and SEC analyses confirmed the effectiveness of the in situ polymerization, yielding structurally regular PBA with narrow molecular weight polydispersity and 7750>M ̅_n>30360 g/mol, depending on the organoclay load. XRD and TEM analyses showed best clay dispersion and homogeneous distribution at 2 wt% 3CTA-BDT. From TGA and DSC results the thermal stability of PBA is greatly improved even at 1 wt% 3CTA-BDT, its glass transition temperature is nearly unaffected while crystallinity is increased by the organoclay nucleating action. These results, along with a bionanocomposite hydrophilicity only moderately higher than that of PBA, make this preparation approach particularly promising

Diversity of Halophyte Desert Vegetation of the Different Saline Habitats in the Valley of Oued Righ, Low Sahara Basin, Algeria

Abstract: The aim of the present study was to investigate the floristic composition and diversity of the different habitat types in the saline areas of the valley of Oued Righ, locating in the low Sahara basin of Algeria. Three distinct saline habitats were examined: saline soil habitats, subsaline soil habitats, and waterlogged habitats. A total of 67 stands along the study area were investigated using the quadrat method, and different vegetation parameters, such as cover, frequency, density, and Importance Value Index (IVI), were recorded. Differences of species diversity and richness between saline habitats were also compared. A total of 38 plant species belonging to 29 genera and 13 families were identified from the three studied habitats. Chenopodiaceae was the predominant family. The majority of the species were of Saharo-Arabian distribution. Chemaephytes had the highest contribution to the life forms spectra. Species composition in the different habitat types showed differences in species richness. Subsaline soil habitats were the most diverse, followed by saline soil habitats. Waterlogged habitats had the lowest diversity. The floristic composition and the dominant species of each habitat were presented. The potential role of the halophyte species was discussed. These findings may lead to a better understanding of the functions, requirements, and sensitivities of these ecosystems

Phosphorylated micro- vs. Nano-cellulose: a comparative study on their surface functionalisation, growth of titanium-oxo-phosphate clusters and removal of chemical pollutants

International audienceControlled cellulose disassembly affords many variants including amorphous micro-sized cellulose crystals (MCC) and cellulose nano-sized crystals (CNC), which have emerged recently as green and sustainable nanomaterials. Unfortunately, their lower reactivity and thermal and chemical instability constitute an impediment for multifaceted nanoscience and nanotechnology usage. Herein, MCC and CNC are functionalised using two phosphorus derivatives (phosphoryl chloride and hexachlorocyclotriphosphazene), under acid-free, urea-free and corrosive-free, gentle experimental conditions. Notably, CNC can accommodate more phosphorus species compared to MCC, with the bulky phosphazene precursor being less reactive in both cases. In contrast, CNC is less prone to post-grafting titanium alkoxide species compared to MCC. Alternatively, phosphorylation circumvents this drawback and enhanced post-grafting reactivity was observed for P-MCC and P-CNC modified cellulose. The presence of phosphorus fragments provides a way of anchoring ultrastable metal oxide clusters on the nanofibrillar surface through metal–phosphonate (P–O–Ti) bridges. Direct condensation of soluble phosphorus reagents with metal alkoxide bearing acetylacetonate fragments constitutes another alternative to grow a substantial amount of metal oxide clusters on both MCC and CNC. The beneficial effect of phosphorus incorporation is convincingly illustrated by their efficiency to scavenge representative anionic and cationic dye pollutants compared to native, non-modified cellulose and its carboxymethylcellulose analogues

An optimized sono-heterogeneous Fenton degradation of olive-oil mill wastewater organic matter by new magnetic glutarlaldehyde-crosslinked developed cellulose

International audienc

Isotropic and Oriented Copper Nanoparticles Supported on Graphene as Aniline Guanylation Catalysts

Adsorption of copper nanoparticles (NPs) on preformed graphene (G) affords an efficient catalyst for the nucleophilic addition of anilines to N,N'-dialkylcarbodiimides to form the corresponding guanidines. Cu/G exhibits a wide scope in promoting guanylation of different substituted anilines and carbodiimides and outperforms Cu nanoparticles supported on carbon nanotubes, active carbon, layered clay, TiO2 and CeO2. Importantly, the performance of the catalyst could be increased by 3 orders of magnitude, reaching TONs of 5.95 x 10(4) and TOFs of 9.9 x 10(2) h(-1) by using as catalysts films of 1.1.1 facet oriented Cu nanoplatelets (3-4 nm thickness and 20-40 nm lateral dimensions) having a strong interaction with G. This enhancement of the catalytic activity derives from the preferential facet orientation of Cu nano platelets and their strong grafting on G. These catalytic results show the potential that G offers as support for metal NPs for the development of highly active recoverable heterogeneous catalysts.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ-2015-69153-C2-R1) is gratefully acknowledged. S.F. thanks the Erasmus Mundus-Maghreb & Egypte (EMMAG) for a fellowship to support her stay at Valencia. Support to S.F. by the National Center for Scientific and Technical Research of Morocco (CNRST) is also acknowledged. A.P. also thanks the Spanish Ministry of Economy and Competitiveness for a Ramon y Cajal research contract.Frindy, S.; El Kadib, A.; Lahcini, M.; Primo Arnau, AM.; García Gómez, H. (2016). Isotropic and Oriented Copper Nanoparticles Supported on Graphene as Aniline Guanylation Catalysts. ACS Catalysis. 6(6):3863-3869. https://doi.org/10.1021/acscatal.6b00995S386338696

Aldehyde-conjugated chitosan-graphene oxide glucodynamers: ternary cooperative assembly and controlled chemical release

Simultaneous condensation of aromatic aldehydes (ArxCHO; x =1–4) on chitosan biopolymer (CS)affords, after water-evaporation, structurally-conjugated aryl-functionalized CS-Arx-ffilms. Similarly, cooperative assembly of two-dimensional nanometric graphene oxide (GO), aromatic aldehyde and chitosan provides transparent, flexible and crack-free aldehyde-functionalized, ternary-reinforced CS-Arx-GO-f nanocomposite films. Homogenous films were obtained using ortho-hydroxybenzaldehyde Ar1 while the para-hydroxybenzaldehyde Ar4 was prone to packing inside. Textural and mechanical properties were investigated and expectedly, sig- nificant improvement was found for CS-Ar1-GO-f because of the great dispersion of the aromatic and the pre- sence of the filler. The sensitivity of unsaturated C]N imine bond to hydrolysis was explored for triggering controlled release of aromatics from the as-prepared films. All of them were found to induce a time-dependent aromatic release. It has been moreover observed that the release was significantly delayed in CS-Arx-GO-f compared to CS-Arx-f, a fact attributed to the interplay of the ring with the basal and edges of graphene oxide, through π-π stacking and additional hydrogen bonding interactions. This finding shows that beyond the con- ventional wisdom using fillers for improving thermal and mechanical properties, the tiny carbon sheets can act as a regulator for aldehyde release, thereby providing a way for more controlled chemical delivery from confined nanocomposites