Mohamed Guerrouache

Functionalization of macroporous organic polymer monolith based on succinimide ester reactivity for chiral capillary chromatography: a cyclodextrin click approach.

Macroporous cross-linked organic polymer based on N-acryloxysuccinimide (NAS) and ethylene dimethacrylate (EDMA) was prepared inside 75 µm id fused silica capillary as a functionalizable monolithic stationary phase for chromatographic applications. Succinimide groups on the monolith surface provide reactive sites able to react readily through standard electrophile-nucleophile chemistry. Propargylamine was used to prepare alkyne functionalized poly(NAS-co-EDMA). Onto this azido-reactive polymer surface was grafted β-cyclodextrin (CD) via a triazole ring utilizing the copper(I)-catalyzed 1,3-dipolar cyclo-addition reaction. Chemical characterization was performed in situ after each synthetic step by means of Raman spectroscopy. Good enantioseparations of flavanone enantiomers, chosen as test chiral compound, were achieved under reversed phase conditions by both capillary electrochromatography and nano-liquid chromatography (nano-LC) techniques. These results demonstrate the potentiality and usefulness of click chemistry in the preparation of β-CD containing chiral organic polymer monolith.

Site-specific immobilisation of gold nanoparticles on a porous monolith surface by using a thiol–yne click photopatterning approach

A monolith surface with alkyne functionality was reacted with cysteamine through radical-mediated thiol-yne addition reaction providing a hydrophilic and chelating interface. Photochemical initiation affords spatial control over the reaction site and further site-specific immobilisation of gold nanoparticles.

Zwitterionic polymeric monoliths for HILIC/RP mixed mode for CEC separation applications

Polymer-based monoliths with zwitterionic surface character were synthesized in capillary columns following a two-step approach to provide versatile electrochromatographic stationary phases exhibiting potentiality of both hydrophilic interaction and RP separation modes. UV-initiated free radical copolymerization of N-acryloxysuccinimide and ethylene dimethacrylate was performed using azobisisobutyronitrile as initiator and toluene as porogen. One of the originalities of this approach relies on the dual role of the N-acryloxysuccinimide monomer that is successively used during the preparation protocol to first covalently graft chromatographic selectors on the monolith surface via simple nucleophilic substitution reaction and then to generate negative charges through hydrolysis of remaining N-hydroxysuccinimide units. In this respect, the grafting of hexyldiamine affords potential cationic surface charges. It is shown that it is possible to tune, controlling the pH of the mobile phase, the intensity and direction of the generated EOF. Moreover, the nature of the interfacial interaction process responsible for the observed separations is well governed by the composition of the mobile phase. Polymer backbone hydrophilization is proposed as an efficient way to improve the HILIC behavior of poly(N-acryloxysuccinimide-co-ethylene dimethacrylate) based monolithic CEC columns together with the grafting of an alkyldiamine incorporating a shorter aliphatic segment.

A first overview of textile fibers, including microplastics, in indoor and outdoor environments.

Studies about microplastics in various environments highlighted the ubiquity of anthropogenic fibers. As a follow-up of a recent study that emphasized the presence of man-made fibers in atmospheric fallout, this study is the first one to investigate fibers in indoor and outdoor air. Three different indoor sites were considered: two private apartments and one office. In parallel, the outdoor air was sampled in one site. The deposition rate of the fibers and their concentration in settled dust collected from vacuum cleaner bags were also estimated. Overall, indoor concentrations ranged between 1.0 and 60.0 fibers/m3. Outdoor concentrations are significantly lower as they range between 0.3 and 1.5 fibers/m3. The deposition rate of the fibers in indoor environments is between 1586 and 11,130 fibers/day/m2 leading to an accumulation of fibers in settled dust (190-670 fibers/mg). Regarding fiber type, 67% of the analyzed fibers in indoor environments are made of natural material, primarily cellulosic, while the remaining 33% fibers contain petrochemicals with polypropylene being predominant. Such fibers are observed in marine and continental studies dealing with microplastics. The observed fibers are supposedly too large to be inhaled but the exposure may occur through dust ingestion, particularly for young children.

Synthesis of new α, α′, β-trisubstituted β-lactones as monomers for hydrolyzable polyesters

Novel α, α′, β-trisubstituted β-lactones have been prepared by a concise and efficient synthesis in five steps from commercial racemic diethyl oxalpropionate. These lactones with different lateral groups can be polymerized or co-polymerized for obtaining polyesters with high molecular weight. Chemical modification of these functionalized hydrolyzable polymers will be used to adjust their properties to the selected temporary applications.

Novel in-capillary polymeric monoliths arising from glycerol carbonate methacrylate for flow-through catalytic and chromatographic applications

In-capillary reactive polymer monoliths have been prepared from glycerol carbonate methacrylate functional monomers. Following functionalization with suitable ligands and eventually after immobilization of metallic nanoparticles, these materials can be successfully employed as supports for chromatographic applications or microreactors for flow-through catalysis.

Synthesis of novel α, α', β-trisubstituted β-lactones

Abstract A concise and efficient synthesis of α,α′,β-trisubstituted β-lactones is presented. These novel lactones are easily obtained in five steps and will be dedicated to anionic ring opening polymerization.

Gold nanoparticles-supported histamine-grafted monolithic capillaries as efficient microreactors for flow-through reduction of nitro-containing compounds

A histamine functionalized monolith was synthesized within a micro-sized channel as a permeable support for the immobilization of 5, 20 and 100 nm-sized gold nanoparticles and the resulting nanostructured hybrid monoliths were applied as microreactors for the catalytic reduction of nitro-derivatives. The whole synthetic pathway of the composite materials relies on (i) UV-induced polymerization of N-acryloxysuccinimide and ethylene glycol dimethacrylate in toluene, (ii) surface grafting of histamine through nucleophilic substitution of hydroxysuccinimide leaving groups, and (iii) specific adsorption of citrate-stabilized colloidal gold nanoparticles. The achievement of the successive synthetic steps was ascertained by using a combination of experimental techniques providing information about the chemical composition (FTIR, Raman, and EDX) and porosity and surface-dispersion (SEM) of gold nanoparticles. Of particular interest, it is shown that surface-grafted histamine units exhibit strong affinity towards gold nanoparticles and allow homogeneous and dense dispersion of 5 and 20 nm sized nanoparticles. Consequently, the gold nanoparticle size-dependence of the catalytic activity (conversion of nitro and di-nitro aromatic compounds into the corresponding amino and di-amino-derivatives) was demonstrated, highlighting the utmost importance of controlling the dispersion of nano-catalysts on the support surface, while histamine protonation was also evidenced as a parameter of paramount importance regarding nanogold surface density and thus resulting catalytic activity. Histamine protonation notably allows the generation of electrostatic interactions between citrate-coated gold nanoparticles and thus-formed positive charges at the monolith surface.

Thiol–ene click chemistry for the design of diol porous monoliths with hydrophilic surface interaction ability: a capillary electrochromatography study

A monolithic material with dual functionality was successfully synthesized through the combination of UV-initiated free radical copolymerization, nucleophilic substitution reaction and thiol–ene radical photoaddition. Firstly, poly(N-acryloxysuccinimide-co-ethylene dimethacrylate) was prepared by non-solvent induced phase separation occurring within the course of the polymerization of the respective monomers. Toluene was selected as a porogen providing percolating pores in the micrometer range. Secondly, N-hydroxysuccinimide units on the monolith surface were converted into ene functionality through covalent immobilization of allylamine. Finally, thioglycerol served as a hydrophilizing agent of the pore surface via surface confined thiol–ene click grafting. All the preparation steps were performed, in situ, i.e. within the confines of UV-transparent capillary channels, affording a micro-column with electro-osmotic flow generation and hydrogen bond forming abilities. Raman microspectrocopy confirmed that all the synthetic steps were accomplished successfully. Investigation of the electrochromatographic retention behavior of hydrophobic and hydrophilic solutes revealed the possibility of tuning the interfacial character of the diol-functionalized monolithic stationary phases with respect to the water content in the surrounding liquid phase. For the acetonitrile-rich mobile phase, the diol-monolith interface exhibited highly hydrophilic character allowing fast and efficient separation of phenol and aniline derivatives, as well as methylxanthines and pyrimidic bases. Moreover, the relative standard deviation of the retention factor values was less than 3.3%.

Photochemically-Driven Methods for the In Situ and Site-Specific Fabrication of Monolithic-Based Electrochromatographic Microsystems

This paper reports on the in-situ synthesis of reactive polymeric monolith and its subsequent surface functionalization. Poly (N-acryloyloxysuccinimide-co-ethylene dimethacrylate) was prepared through free radical photopolymerization of the respective monomers. The grafting procedure is based on the preliminary grafting of alkyne units on the monolith surface and the further radical photoaddition of functional thiol molecules. Implementation of UV-driven polymerization and grafting methods enabled the locally controlled immobilization of generic monolith within the confines of the capillary channel, and the site-specific immobilization of ligands on the pore surface of the monolith. Our results suggest that such a synthesis methodology is promising for integrating multiple analytical modules within microstructures for on-line analysis.