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See detailOptimisation de l'acylation enzymatique du mannose par l'utilisation de co-solvants
Brognaux, Alison ULg; Favrelle, Audrey ULg; Deleu, Magali ULg et al

Poster (2009, October 15)

Les esters de sucres sont des surfactants non-ioniques avec de nombreuses applications dans l’industrie alimentaire et pharmaceutique. La synthèse enzymatique est généralement préférée à la synthèse ... [more ▼]

Les esters de sucres sont des surfactants non-ioniques avec de nombreuses applications dans l’industrie alimentaire et pharmaceutique. La synthèse enzymatique est généralement préférée à la synthèse chimique. En effet, cette dernière consomme beaucoup d’énergie, est moins sélective envers les différents groupes hydroxyle du sucre et conduit à des produits de caramélisation. Le type de solvant, le ratio sucre / lipide, la température et le type de lipase immobilisée peuvent être modifiés afin d’optimiser la vitesse initiale et le rendement de réaction. Les travaux décrits rapportent l’optimisation de la synthèse enzymatique de myristate de mannosyle à partir de mannose et d’acide myristique en présence de la lipase de Candida antarctica B (Novozyme 435). Les concentrations optimales en mannose et en acide myristique sont respectivement de 0,1 et 0,6 M dans du tert-butanol pur à 60°C. Ces conditions conduisent à une vitesse initiale de 1,3 g/l.h pour 2 g/l d’enzyme et à un rendement molaire de 55%. Afin d’améliorer cette vitesse initiale de réaction, différents mélanges de tert-butanol et de co-solvants polaires ont été testés. Les solvants polaires (log P faibles) augmentent la solubilité des sucres mais provoquent l’inactivation partielle des lipases. Lorsque le log P est supérieur à 3, l’enzyme reste active mais ce type de milieu n’est pas approprié si les deux substrats diffèrent grandement en terme de polarité. Le but de cette étude est donc de trouver un compromis entre la solubilité du sucre et le maintient de l’activité enzymatique. Les quatre co-solvants testés sont le DMSO, le DMF, le formamide et la pyridine. Au terme de ce travail, le DMSO, à raison de 10 % dans le milieu réactionnel, s’est avéré être le meilleur co-solvant parmi ceux testés. Dans ces conditions, la vitesse initiale de réaction est accrue de 130 %. [less ▲]

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See detailPréparation de nouveaux copolymères amphiphiles mannosylés d'architecture greffée et caractérisation par QCM-D
Freichels, Hélène ULg; Broze, Guy; Alaimo, David ULg et al

Conference (2009, October 14)

Durant les dernières décennies, le domaine pharmaceutique s’est intéressé aux micelles et nanoparticules polymères celles-ci pouvant être utilisées comme vecteurs à libération contrôlée. Dans ce domaine ... [more ▼]

Durant les dernières décennies, le domaine pharmaceutique s’est intéressé aux micelles et nanoparticules polymères celles-ci pouvant être utilisées comme vecteurs à libération contrôlée. Dans ce domaine, des copolymères amphiphiles combinant le poly(oxyde d’éthylène) (POE), polymère possédant des propriétés répulsives vis-à-vis des protéines plasmiques, et la poly-epsilon-caprolactone (PCL), un polyester aliphatique, polymère hydrophobe biocompatible et biodégradable permettant l’incorporation d’un principe actif hydrophobe, sont d’excellents candidats pour cette d’application. Jusqu’à présent, ce type de copolymère amphiphile principalement étudié est d’architecture linéaire. Récemment, notre laboratoire a développé une stratégie permettant la préparation de nouveaux copolymères greffés, composés d’un squelette principal de PCL et de greffons de POE. De plus, des agents de ciblage peuvent être introduits à l’extrémité du POE de ces copolymères amphiphiles, faisant de ceux-ci des candidats idéaux comme vecteur de troisième génération, permettant un ciblage spécifique au sein même de l’organisme. Le mannose est un agent intéressant, car il est reconnu à la surface des cellules dendritiques. Dans ce travail, la préparation de copolymères greffés fonctionnalisés par du mannose est décrite. La présence de mannose à la surface des micelles a d’abord été mise en évidence par test ELLA (Enzyme Linked Lectin Assay). Ensuite une étude plus approfondie a été réalisée par QCM-D (Microbalance à Cristal de Quartz avec Dissipation). Cette technique originale permet de mettre en évidence l’interaction entre la lectine immobilisée sur la surface du cristal de la microbalance et le mannose exposés à la périphérie des micelles du copolymère. [less ▲]

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See detailRecent advances in the functionalization of aliphatic polyesters by ring-opening polymerization
Lecomte, Philippe ULg; Jérôme, Christine ULg

in Khosravi, Ezat; Yagci, Yusuf; Savelyev, Yuri (Eds.) New smart materials via metal mediated macromolecular engineering (2009)

Two main strategies aiming at synthesizing aliphatic polyesters bearing pendant functional groups will be reported. The first one is based on the synthesis and the polymerization of lactones substituted ... [more ▼]

Two main strategies aiming at synthesizing aliphatic polyesters bearing pendant functional groups will be reported. The first one is based on the synthesis and the polymerization of lactones substituted by various functional groups. The direct grafting of functional groups onto aliphatic polyesters is the second strategy. Last but not least, the association of these two strategies is very promising in order to overcome their respective limitations. [less ▲]

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See detailSynthesis of functionalized polyesters by the "click" copper-catalyzed alkyne-azide cycloaddition
Lecomte, Philippe ULg; Riva, Raphaël ULg; Jérôme, Christine ULg

in Khosravi, Ezat; Yagci, Yusuf; Savelyev, Yuri (Eds.) New smart materials via metal mediated macromolecular engineering (2009)

The functionalization of aliphatic polyesters by the copper-mediated azide–alkyne Huisgen’s cycloaddition is very efficient under mild conditions, which prevents degradation from occurring. The ... [more ▼]

The functionalization of aliphatic polyesters by the copper-mediated azide–alkyne Huisgen’s cycloaddition is very efficient under mild conditions, which prevents degradation from occurring. The implementation of this reaction requires the synthesis of aliphatic polyesters bearing pendant alkynes and azides, which can be carried out either by polycondensation or by ring-opening polymerization. [less ▲]

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See detailα-chloro-ε-caprolactone, a versatile precursor for grafting of aliphatic polyesters
Riva, Raphaël ULg; Lenoir, Sandrine ULg; Lecomte, Philippe ULg et al

Poster (2009, September 17)

Macromolecular engineering is one of the most powerful tool to synthesise many polymers of various architectures and with tailored properties. This contribution aims at reporting on a novel strategy for ... [more ▼]

Macromolecular engineering is one of the most powerful tool to synthesise many polymers of various architectures and with tailored properties. This contribution aims at reporting on a novel strategy for the macromolecular engineering of poly-ε-caprolactone (PCL) which is based on the use of a dual monomer / initiator compound, α-chloro-ε-caprolactone (αClεCL). Indeed, αClεCL is not only polymerizable by ring opening initiated by metal alkoxides, but it is also an initiator for the atom transfer radical polymerization (ATRP) of vinyl monomers, so leading easily to the synthesis of macromonomers. Polystyrene macromonomer has been prepared by this method and successfully copolymerized with ε-caprolactone (εCL) with formation of the corresponding grafted PCL. αClεCL is also a precursor of copolyesters with εCL that bear pendant chlorides. These (co)polyesters have been used as macroinitiators for the ATRP of methyl methacrylate in order to synthesise the corresponding graft copolymer. On the other hand, the pendant chlorides of poly(αClεCL-co-εCL) copolyesters were easily converted into azide with formation of the corresponding azide bearing copolyester. This copolyester was then reacted with an alkyne bearing an ATRP initiator by “Click chemistry”. The conversion of chlorides into more efficient ATRP initiators led to the improvement of the initiation efficiency of the macroinitiator. [less ▲]

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See detailCobalt mediated radical polymerization (CMRP) using bis(acetylacetonato)cobalt(II): a unique tool for controlling the radical polymerization of conjugated and unconjugated vinyl monomers
Hurtgen, Marie ULg; Debuigne, Antoine ULg; Jérôme, Christine ULg et al

Poster (2009, September 17)

Cobalt-Mediated Radical Polymerization (CMRP) imparts a high level of control on the polymerization of acrylic and vinylic esters, acrylic acid and acrylonitrile. However, each class of monomers appears ... [more ▼]

Cobalt-Mediated Radical Polymerization (CMRP) imparts a high level of control on the polymerization of acrylic and vinylic esters, acrylic acid and acrylonitrile. However, each class of monomers appears to be controlled by one class of cobalt complexes. For example, the polymerization of acrylates and acrylic acid is mediated by cobalt porphyrin complexes while vinyl acetate (VAc) and acrylonitrile are efficiently controlled by bis(acetylacetonato)cobalt(II) (Co(acac)2). Therefore, a challenging issue in CMRP remains to broaden the range of monomers that can be controlled by the same cobalt complex. Recently, the controlled random copolymerization of butyl acrylate (BuA) with VAc was performed using the conventional V-70/Co(acac)2 CMRP system, but the homopolymerization of BuA remained uncontrolled. In this work, we used a new alkylcobalt(III) adduct to initiate and control the copolymerization of BuA with VAc. This achievement resulted in a significant improvement over the V-70/Co(acac)2 pair regarding the molecular weight control and the polydispersity indexes. Moreover, for the first time, the alkylcobalt(III) adduct was also efficient in controlling the homopolymerization of BuA and yielded low polydispersity PBuA even in the absence of VAc. These results indicate that Co(acac)2 is a versatile mediator for the CMRP of both unconjugated vinyl monomers (VAc, N-vinylpyrrolidone) and conjugated monomers such as acrylates. It gives access to copolymers that cannot be prepared by other controlled radical polymerization techniques. [less ▲]

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See detailCobalt-mediated radical polymerization of vinyl monomers: investigation of cobalt-coordination
Debuigne, Antoine ULg; Piette, Yasmine ULg; Poli, Rinaldo et al

Poster (2009, September 17)

Controlled Radical Polymerization techniques have been developed to obtain well-defined architectures and to control polymer parameters. Among these systems is Cobalt-Mediated Radical Polymerization (CMRP ... [more ▼]

Controlled Radical Polymerization techniques have been developed to obtain well-defined architectures and to control polymer parameters. Among these systems is Cobalt-Mediated Radical Polymerization (CMRP), which is based on the reversible deactivation of the growing radical chains with a cobalt complex, the cobalt (II) bis(acetylacetonate). The interest of this system is not only due to its ability to control the polymerization of very reactive monomers such as vinyl acetate (VAc) and N-vinylpyrrolidone (NVP), but also its peculiar mechanism which exhibits two pathways depending on the polymerization conditions; a reversible termination process and a degenerative chain transfer mechanism. Furthermore, it has been showed that the Co-C bond strength and thus the polymerization are strongly influenced by the use of some additives, such as water, dimethylformamide, dimethylsulfoxide and pyridine, which coordinate the cobalt free site. In this presentation we report the use of a preformed alkyl-cobalt(III) adduct as initiator for the polymerization of various vinyl monomers of different reactivity (VAc, acrylonitrile,…) and on the effect of several ligands on their polymerization control. The preparation of novel block copolymers by CMRP will finally be presented. As a conclusion, cobalt-coordination appears today as a unique opportunity to adjust the Co-C bond strength and to push back the bounds of possibilities in terms of macromolecular engineering assisted by CMRP. [less ▲]

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See detailNew perfulorinated macroligand for the implementation of dispersion atom transfer radical polymerization in sc CO2
Grignard, Bruno ULg; Calberg, Cédric ULg; Jérôme, Christine ULg et al

Poster (2009, September 17)

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical ... [more ▼]

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical polymerization (CRP) in scCO2 has started to gain attention. Among all the controlled processes, Atom Transfer Radical Polymerization has emerged as a robust tool for the preparation of polymers with well-defined molecular weight, architecture and chain-end functionality. In a very recent paper, we reported the first efficient dispersion ATRP of methyl methacrylate (MMA) in scCO2 using a fluorinated polymeric ligand that had a dual role, i.e., the complexation of the copper salt and the stabilization of PMMA growing particles. In this contribution, we extended this new system to the dispersion ATRP of styrene2, to the synthesis of diblock copolymers beads2 or to the preparation of PMMA particles by AGET ATRP. Because both ATRP and alkyne-azide Huisgen’s 1,3-dipolar cycloaddition relies on the use of a Cu(I) catalyst, synthesis of pyrene end-functionalized polymers by simultaneous dispersion ATRP and click reaction was also investigated in supercritical carbon dioxide. Finally, the immobilization of these new macroligands onto an inorganic support leads to the formation of pseudo-homogeneous catalyst that were successfully used to prepare CO2-soluble perfluorinated methacrylate and depending on the molecular weight and TEDETA composition of the macroligand, results obtained by supported ATRP without addition of Cu(II) as deactivator are identical to those obtained by homogeneous ATRP. [less ▲]

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See detailIn situ formation of stabilizers for the implementation of dispersion nitroxide mediated polymerization of MMA in supercritical carbon dioxide
Grignard, Bruno ULg; Gigmes, Didier; Jérôme, Christine ULg et al

Poster (2009, September 17)

Controlled dispersion Nitroxide Mediated Polymerization (NMP) of methyl methacrylate (MMA) was successfully carried out for the first time in supercritical carbon dioxide (scCO2) in the presence of CO2 ... [more ▼]

Controlled dispersion Nitroxide Mediated Polymerization (NMP) of methyl methacrylate (MMA) was successfully carried out for the first time in supercritical carbon dioxide (scCO2) in the presence of CO2-philic perfluorinated surfactant that was generated “in situ”. The control of the MMA polymerization relies on the strategy developed by Charleux et al. that consists of using a SG1-based alkoxyamine, i.e. the block-builder, in the presence of small amount of styrene. In a first step, CO2 soluble polyheptadecafluorodecylacrylate was prepared in scCO2 using block-builder as an alkoxyamine. In a second step, nitroxide SG1 mediated dispersion polymerization of MMA was conducted at 70°C and 300 bar in the presence of 5 w% of SG1 terminated surfactant compared to the monomer. Different monomer to alkoxyamine molar ratios were investigated in order to target different molecular weights. In each case, the monomer conversion was high (>90 %), the experimental molecular weight was in good agreement with the theoretical value and the polydispersity was narrow (Mw/Mn ~1.2). Moreover, after depressurisation of the cell, PMMA was collected as a free flowing powder consisting of small sized microspheres. [less ▲]

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See detailSynthesis of novel block copolymers by cobalt-mediated radical polymerization (CMRP) and isoprene-assisted radical coupling reaction (I-ARC)
Debuigne, Antoine ULg; Jérôme, Christine ULg; Detrembleur, Christophe ULg

Conference (2009, September 17)

Nowadays, progresses in medicine, biotechnology, microelectronic and many other fields are more and more sustained by the development of novel polymer materials with constantly improved properties and ... [more ▼]

Nowadays, progresses in medicine, biotechnology, microelectronic and many other fields are more and more sustained by the development of novel polymer materials with constantly improved properties and well-defined molecular parameters. In this context, we designed an innovative and very promising tool for macromolecular engineering. This technique, called Isoprene-Assisted Radical Coupling (I-ARC), allows to couple quantitatively polymer chains preformed by Cobalt-Mediated Radical Polymerization (CMRP), an efficient controlled radical polymerization system for vinyl acetate (VAc) and acrylonitrile (AN). Typically, addition of isoprene to well-defined polymers prepared by CMRP invariably leads to the quantitative coupling reaction of the chains, as assessed by the perfect doubling of the molar mass of the polymer. Importantly, the I-ARC reaction is not limited to macromolecules with low molar masses and homopolymers, contrary to the previously reported radical chains coupling methods. Indeed, when applied to diblock copolymers, I-ARC constitutes a straightforward approach for the synthesis of telechelic symmetrical ABA triblock copolymers, as illustrated by the preparation of poly(vinyl acetate)-b-poly(acrylonitrile)-b-poly(vinyl acetate) triblock copolymers and their derivatives. [less ▲]

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See detailFoams of polyurethane/MWNT nanocomposites for efficient EMI reduction
Chen, Y. Y.; Urbanczyk, Laetitia ULg; Thomassin, Jean-Michel ULg et al

Poster (2009, September 16)

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See detailKey role of metal-coordination in cobalt-mediated radical polymerization of vinyl acetate
Debuigne, Antoine ULg; Poli, Rinaldo; Jérôme, Robert ULg et al

in Matyjaszewski, Krzysztof (Ed.) Controlled/living radical polymerization: progress in RAFT, DT, NMP & OMRP (2009)

Cobalt mediated radical polymerization (CMRP) of vinyl acetate (VAc) follows a reversible termination mechanism when initiated from a preformed alkyl-cobalt(III) complex. In these particular conditions ... [more ▼]

Cobalt mediated radical polymerization (CMRP) of vinyl acetate (VAc) follows a reversible termination mechanism when initiated from a preformed alkyl-cobalt(III) complex. In these particular conditions, CMRP functions as a stable free radical process and fine tuning of the Co-C bond strength becomes crucial. Increase of temperature and addition of molecules, such as water, dimethylformamide and dimethylsulfoxide, able to coordinate the cobalt complex appeared as efficient strategies to weaken the Co-C bond and thus to speed up the polymerization while maintaining a very good control of the VAc polymerization. The key role of metal-coordination was investigated by kinetic measurements combined with DFT calculations. [less ▲]

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See detailGold-loaded carbon nanoparticles from poly(vinyl alcohol)-b-poly(acrylonitrile) non-shell-cross-linked micelles
Bryaskova, Rayna; Willet, Nicolas ULg; Duwez, Anne-Sophie ULg et al

in Chemistry : An Asian Journal (2009), 4(8), 1338-1345

Herein we show that a new amphiphilic poly(vinyl alcohol)-b-poly(acrylonitrile) block copolymer dispersed in water can be easily loaded with gold nanoparticles by addition of chlorauric acid followed by ... [more ▼]

Herein we show that a new amphiphilic poly(vinyl alcohol)-b-poly(acrylonitrile) block copolymer dispersed in water can be easily loaded with gold nanoparticles by addition of chlorauric acid followed by reduction by sodium borohydride. After deposition of the so-loaded micelles onto a silicon wafer, followed by an appropriate thermal treatment, the poly(acrylonitrile) core of the micelles is carbonized, while the poly(vinyl alcohol) shell is completely decomposed and volatilized, leading to gold encapsulated in carbon nanoparticles. The morphology of the micelles is maintained during thermal treatment without requiring shell-cross-linking of the micelles prior to pyrolysis. [less ▲]

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See detailElectrografting method for forming and regulating a strong adherent nanostructured polymer coating
Jérôme, Robert ULg; Jérôme, Christine ULg; Serwas, Harry et al

Patent (2009)

Electrografting method for forming and regulating a strongly adherent nanostructured polymer coating onto an electro-conductive surface profile characterized in that the surface profile is regulated by ... [more ▼]

Electrografting method for forming and regulating a strongly adherent nanostructured polymer coating onto an electro-conductive surface profile characterized in that the surface profile is regulated by electrodeposition of nanometre- and/or micrometre-scale nuclei onto the surface profile prior to or simultaneously to the formation of the polymer coating. [less ▲]

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See detailUnusual quantitative (co)polymer chain coupling reaction based on isoprene and cobalt complexes
Debuigne, Antoine ULg; Jérôme, Christine ULg; Detrembleur, Christophe ULg

Conference (2009, July 15)

Nowadays, progresses in medicine, biotechnology, microelectronic and many other fields are more and more sustained by the development of novel polymer materials with constantly improved properties and ... [more ▼]

Nowadays, progresses in medicine, biotechnology, microelectronic and many other fields are more and more sustained by the development of novel polymer materials with constantly improved properties and well-defined molecular parameters. In this context, we designed an innovative and very promising tool for macromolecular engineering. This technique, called Isoprene-Assisted Radical Coupling (I-ARC), allows to couple quantitatively polymer chains preformed by Cobalt-Mediated Radical Polymerization (CMRP), an efficient controlled radical polymerization system for vinyl acetate (VAc) and acrylonitrile (AN). Typically, addition of isoprene to well-defined polymers prepared by CMRP invariably leads to the quantitative coupling reaction of the chains, as assessed by the perfect doubling of the molar mass of the polymer. Importantly, the I-ARC reaction is not limited to macromolecules with low molar masses and homopolymers, contrary to the previously reported radical chains coupling methods. Indeed, when applied to diblock copolymers, I-ARC constitutes a straightforward approach for the synthesis of telechelic symmetrical ABA triblock copolymers, as illustrated by the preparation of poly(vinyl acetate)-b-poly(acrylonitrile)-bpoly(vinyl acetate) triblock copolymers and their derivatives. [less ▲]

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See detailEnzymatic modifications of sugar in supercritical carbon dioxide
Favrelle, Audrey ULg; Brognaux, Alison ULg; Debuigne, Antoine ULg et al

Poster (2009, July 07)

Carbohydrates esters are non-ionic surfactants that have a wide range of commercial applications in cosmetic, food and pharmaceutical industry. They are produced from renewable and inexpensive raw ... [more ▼]

Carbohydrates esters are non-ionic surfactants that have a wide range of commercial applications in cosmetic, food and pharmaceutical industry. They are produced from renewable and inexpensive raw materials, are bio-degradable and non-toxic. Chemical synthesis of sugar esters is generally performed at a high temperature in the presence of an alkaline catalyst lead-ing to a mixture of products. In this respect, the corresponding enzyme-catalyzed processes in non-conventional media are more selective. For this purpose, lipases are the most useful enzymes. Moreover, supercritical carbon dioxide (SC-CO2) constitutes an interesting alternative to the organic solvents used in the domain as it is considered to be environmentally frien-dlier and safer. For example, its use reduces the contamination of the final products with residual solvents. This property is particularly valued in food, cosmetic and pharmaceutical industry. Our work consists to carry out lipase catalyzed sugar modifications in SC-CO2 and to compare the results with those obtained in organic solvents. The effect of these two different media on the enzyme stability and the yield will be described here. Moreover, the impact of various factors such as pressure, temperature, enzyme form (free or immobilized), use of co-solvent, on the course of the sugar esterification will be discussed. [less ▲]

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See detailOrganoclays prepared in supercritical CO2: implication of onium stability on the properties of PA6 nanocomposites
Naveau, Elodie ULg; Calberg, Cédric ULg; Detrembleur, Christophe ULg et al

Conference (2009, June 23)

The organomodification of layered silicates via our patented supercritical CO2 ion-exchange process, enables the use of a large variety of surfactants, among which phosphonium and ammonium ions of the ... [more ▼]

The organomodification of layered silicates via our patented supercritical CO2 ion-exchange process, enables the use of a large variety of surfactants, among which phosphonium and ammonium ions of the very same structure. The as-obtained organoclays were melt blended with PA6 and the morphology as well as the fire properties of the nanocomposites were studied. With the same degree of nanodispersion, longer ignition times were observed with phosphonium-modified clays compared to ammonium-modified clays. [less ▲]

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