Michel Morcellet

Sorption of aromatic compounds in water using insoluble cyclodextrin polymers

Insoluble β-cyclodextrin (β-CD) polymers have been used for the recovery of various organic pollutants from aqueous solutions. These resins have been prepared by polymerization using epichlorohydrin (Epi) as a crosslinking agent. Several crosslinked polymers with various degrees of β-CD were used. Several studies (time, concentration, kinetics, and pH) are presented here. The results show that these sorbents exhibit high sorption capacities toward substituted benzene derivatives. The mechanism of sorption is both physical adsorption in the polymer network and/or the formation of an inclusion complex and/or the formation of hydrophobic guest–guest interactions.

Grafting of cyclodextrins onto polypropylene nonwoven fabrics for the manufacture of reactive filters. I. Synthesis parameters

A novel method for the preparation of immobilized α-, β-, and γ-cyclodextrins (α-, β-, or γ-CD) on polypropylene (PP) nonwoven fabrics is presented. These new materials were prepared by graft-polymerization of glycidyl methacrylate (GMA) onto PP filters using the electron-beam technique, followed by coupling of α-, β-, and γ-CDs with the epoxide group. Optimization of various reaction parameters such as time, temperature, irradiation dose, monomer, and CD concentration was carried out.

Preparation and sorption properties of a β‐cyclodextrin‐linked chitosan derivative

(3-Cyclodextrin (β-CD) was coupled to chitosan by the intermediate of its monochlorotriazinyl derivative, called βW7MCT, so that a chitosan derivative bearing cyclodextrin was obtained. Because the average degree of substitution of the cyclodextrin derivative was 2.8, the reaction yielded crosslinked insoluble products. The structure of these materials has been investigated by high-resolution magic-angle spinning (HRMAS) with gradients. For the first time, HRMAS spectra of chitosan polymers containing β-CD were obtained. This NMR technique produced one- and two-dimensional well-resolved solid-state spectra. These data confirm the proposed structure. Decontamination of waters containing textile dyes were carried out with the crosslinked derivatives. These tests showed that the new chitosan derivatives are characterized by a rate of sorption and a global efficiency superior to that of the parent chitosan polymer and of the well-known cyclodextrin-epichlorohydrin gels.

Chitosan N-benzyl sulfonate derivatives as sorbents for removal of metal ions in an acidic medium

We synthesized chitosan-based sorbents for the uptake of metal cations in acidic solutions. Chitosan was reacted with 2-formylbenzene sodium sulfonate and 4-formyl-1,3-benzene sodium disulfonate in the presence of NaCNBH3 to yield N-benzyl mono- and disulfonate derivatives of chitosan. IR and NMR spectra confirmed the presence of benzyl sulfonate groups. The degrees of substitution of the monosulfonate chitosan derivatives were in the range of 80%, while those of disulfonate derivatives were about 50%. These sulfonate derivatives of chitosan were tested on the sorption of heavy metals Cd2+, Zn2+, Ni2+, Pb2+, Cu2+, Fe3+, and Cr3+. The sorption capacities for disulfonate compounds were better than for monosulfonate compounds. This phenomenon was attributed to the amphoteric character of the monosulfonate derivatives. To improve the capacity of adsorption of monosulfonate compounds, the amino groups of these compounds were protected by the benzyloxycarbonyl groups. The protection of amino groups of disulfonate derivatives by benzyloxycarbonyl also improved their sorption capacity. The resulting protected polymers were tested for sorption of heavy metals. Both protected polymers were more efficient than are the parent nonprotected polymers. The synthesized sulfonate derivatives of chitosan are especially adapted to the sorption of heavy metals from the acidic industrial effluents.

SOLID STATE NMR SPECTROSCOPY STUDY OF MOLECULAR MOTION IN CYCLOMALTOHEPTAOSE (BETA -CYCLODEXTRIN) CROSSLINKED WITH EPICHLOROHYDRIN

Dry and hydrated insoluble cyclomaltoheptaose (beta-cyclodextrin, beta-CD) polymers have been investigated by solid state 13C NMR spectroscopy techniques such as cross polarization/magic angle spinning with dipolar decoupling (CP/MAS), magic angle spinning both with (DD-MAS) and without (MAS) dipolar decoupling and CP/MAS dipolar dephasing (dd-CP/MAS) to allow the assignment of the main 13C signals. In the solid state, the presence of water in the samples resulted in a better resolution reflecting increased mobility. Two distinct components (crosslinked beta-CD and polymerized epichlorohydrin) have been found. The molecular mobility of these two components has been analyzed in terms of relaxation parameters such as 13C spin lattice relaxation (T1) and 1H spin lattice relaxation in the rotating frame (T1 rho). The T1 values of the polymers show that the beta-CD trapped inside the polymers does not seem to undergo changes in its mobility whatever the amount of epichlorohydrin. The addition of water to beta-CD significantly increases the T1 values reflecting strong interaction between beta-CD and the solvent. The T1P values obtained reflect the homogeneous nature of the materials.

Finishing of Polyester Fabrics with Cyclodextrins and Polycarboxylic Acids as Crosslinking Agents

CDs were grafted onto PET fibers by the intermediate of polycarboxylic acids thatplayed the role of crosslinking agents. We evidenced that grafting occurred despitethat no reaction could happen between the polycarboxylic acids and PET. It wasconcluded that the mode of grafting occurred through the formation of a crosslinkedcopolymer between PCA and CDs. This copolymer was not covalently fixed to thefibers, but physically adhered or was entangled into the fibrous network so that grafting was resistant to washings and was permanent. We report that the grafting rate depended on (i) temperature of curing; (ii) time of curing; (iii) the ratio PCA/CD. In the most drastic conditions, the weight increase of the fabrics due to the graft reaction could reach 25–30%-wt. α, β, γ-CDs and HP-β-CD successfully reacted but not RAMEB because of its reduced number of free hydroxyl groups available for the esterification reaction.

Synthesis and Characterization of Silica Gels Functionalized with Monochlorotriazinyl β-Cyclodextrin and their Sorption Capacities towards Organic Compounds

Different supports, containing a new derivative ofβ-cyclodextrin – monochlorotriazinylβ-cyclodextrin (β-CDMCT) – used forthe reduction of pollutants in waste water, have beenprepared. They are based on silica gel, initially eithercoated with polyethyleneimine (PEI) or grafted with3-aminopropyltrimethoxysilane, functionalized in asecond step with β-CDMCT. In order to obtainsorbents with high β-cyclodextrin content andmaximum accessibility of the β-CD cavity, thefuntionalization was studied while varying experimentalconditions. Thermogravimetry, Raman spectroscopy,specific surface area and pore size distribution were usedfor the characterization of supports. Sorption experimentsshow that these sorbents have sorption capacities towardssome organic pollutants. The mechanism of sorption is bothphysical adsorption in the polymer network (for supportsobtained by coating) and/or the formation of an inclusioncomplex between β-CDMCT and guest molecules.

Complexes of poly(acrylic acid) with some divalent, trivalent and tetravalent metal ions

Abstract The formation of metal complexes between poly(acrylic acid) and divalent, trivalent and tetravalent metal ions was studied. For divalent and pseudodivalent metal ions, the stability constants determined according to the method of Gregor et al. [J. Phy. Chem. 59 (1954) 34] are in the order Cu 2+ >VO 2+ >Co 2+ >Ni 2+ , Zn 2+ . The values were nearly insensitive to the ligand to metal concentration ratio in the range R =1–10. Trivalent and tetravalent ions also induced a strong decrease of the pH but stability constants could not be determined from the formation curves. The metal ions were divided in four groups depending on the shape of the curve Δ pH vs α . These groups differ from one another by (i) the speed of water exchange or (ii) by the speed of ligand exchange in the coordination sphere of the metal in the case of lanthanides.

Capture and Controlled Release of Fragrances by CD Finished Textiles

Cotton, wool and polyester fabrics finished with cyclodextrins (by the intermediateof polycarboxylic acids) were impregnated with six different fragrant molecules(β-citronellol, camphor, menthol, cis-jasmone, benzyl acetate, geraniol) and citronella oil. The smell intensity of the samples has been investigated during almostone year. In most cases, the odour retention of untreated textiles towards the substratesdid not persist over one or two weeks. By contrast, most of the treated sampleskept smelling one year after the beginning of the experiment. We observed that theuse of polyacrylic acid as crosslinking agent was less effective than citric andbutanetetracarboxylic acids. The efficiency of the different CDs varied in the orderγ-CD > β-CD > α-CD, and the durability of the fragranteffect was directly dependent on the amount of CD grafted onto the fabrics.

Separation of structural isomers using cyclodextrin-polymers coated on silica beads

SummarySeveral β-cyclodextrin (CD)-bonded stationary phases for high performance liquid chromatography (HPLC) were prepared, based on silica beads coated with a poly(alkylamine), [poly(ethyleneimine)(PEI)]. In order to obtain stationary phases with a high content of CD and maximum accessibility of the CD cavity, the functionalization was carried out after the coating, using the mono-tosyl derivative of CD as the intermediate. The ability of these supports to separate ortho, meta and para isomers of some disubstituted benzene derivatives was examined. The contribution of the amino groups of the polymer and of the CD cavity to the separation process is discussed. The resolution is mainly based on the difference in the stability of the complexes of the various isomers with CD. The influence of the amount of CD on the height of the theoretical plate is also studied.