Study of the interactions of organic sulfides with active species in the cationic polymerization of 1,3-pentadiene

Different alkyl sulfides (dimethylsulfide, ditertiobutylsulfide and diphenylsulfide) were investigated in the polymerization of 1,3-pentadiene initiated by aluminum trichloride in polar solvent in order to control the polymerization and to study the interaction between the electron donor and the active species. Thus, it was found that dimethylsulfide totally inhibited the polymerization, while thanks to its steric hindrance the polymerization occurred in the presence of ditertiobutylsulfide. However, for this electron donor, a transfer activity was evidenced at room temperature and at 0degreesC, which contributes to prevent the control of the polymerization. Diphenylsulfide stabilizes a little the active centers with nearly no transfer reaction. However in the studied experimental conditions, the stabilization was not sufficient to obtain a living polymerization

Anionic ring-opening polymerization of ethylene oxide in DMF with cyclodextrin derivatives as new initiators

International audienceAnionic polymerization initiated by cyclodextrins suffers from a poor solubility of those derivatives in standard polymerization solvents. The possibility to perform ethylene oxide polymerization initiated by monofunctional initiators (allyl alcohol, 2-methoxyethanol) by living ring opening polymerization in DMF, a good solvent for any CD derivative, was demonstrated by SEC, 1H and 13C NMR analyses. The study was extended to the use of native CD as initiator, leading to the synthesis of ill-defined structures, explained by the reactivity scale of the various hydroxyl functions. Two selectively modified CD derivatives are then used to synthesize a new family of star-shaped poly(ethylene oxide) polymers with CD core, having 14 or 21 arms. The polymerization was found to be living and DOSY experiments confirmed the well-defined structures for the synthesized star-polymers

Supramolecular assemblies of histidinylated α-cyclodextrin in the presence of DNA scaffold during CDplexes formation.

International audienceα-Cyclodextrin was transformed in a cationic unit after per substitution with histidine (His-α-CD) and lysine (Lys-α-CD) molecules on the primary face. His-α-CD and Lys-α-CD were used to form electrostatic complexes (CDplexes) with a plasmid DNA encoding luciferase gene, and the ability of CDplexes to transfect mammalian cells was examined using HEK293-T7 cells. The luciferase activity in cells transfected with His-α-CDplexes was 8-fold higher than that obtained Lys-α-CDplexes. When the transfection was carried out in the presence of chloroquine, the luciferase activity with His-α-CDplexes and Lys-α-CDplexes increased 6 and 25 times, respectively. The lower enhancement with His-α-CDplexes confirmed that histidine induced a proton sponge effect inside endosomes upon imidazole protonation, favoring DNA delivery in the cytosol. At the same time, we found that the condensation of DNA with His-α-CD was unexpectedly stronger than that obtained with the lysyl-α-CD counterpart. Moreover, it was as strong as that observed with high molecular weight polylysine. NMR (ROESY and DOSY) investigations in the absence of DNA showed that an inclusion complex is formed between the imidazole ring of histidine and the hydrophobic cavity of CD but no His-α-CD polymers can be formed by intermolecular interactions. These results suggest that intermolecular interactions between imidazole and His-α-CD cavity could be involved to form supramolecular assemblies in the presence of a DNA scaffold leading to DNA condensation into low diameter particles

Biomimetic artificial ion channels based on beta-cyclodextrin

International audienceStar polymers based on β-cyclodextrin were synthesized by a “click-chemistry” process and characterized by NMR, SEC and BLM. The resulting triazole functional groups create, at a specific pH range, electrostatic hindrance between pores inserted in lipid bilayers, preventing their aggregation, allowing formation of well-defined isolated unitary pores and mimicking biological natural channels

Condensation of alkoxysilanes in alcoholic media: I. Oligomerization of dimethyldiethoxysilane

International audienceIn the context of the preservation of cultural heritage, the treatment of paper by an aminoalkylalkoxysilane, or its mixturewithdimethyldiethoxysilane, has given encouraging results. Diluting the monomer bearing the amino function could contributeto obtaining a flexible network interpenetrating the fibre network. Due to the complexity of the system, the work presentedhere begins with a study of dimethyldiethoxysilane condensation under the conditions used for the paper deacidification(alcoholic medium, neutral condition, etc.). No detectable exchange reaction with ethanol was observed in anhydrous systemsof dimethyldiethoxysilane for 24 h, but in the presence of water, hydrolysis and exchange were observed, the rate constant ofthe former being higher than that of the latter by one order ofmagnitude. Inmethanol, in the presence of water, condensationleading to dimerization was observed within less than three days, with polycondensation requiring a much longer time. Fromthe rate constantmeasurements, inthepresence of water, it appears that thecondensation reaction is the slowest reaction. It canbe concluded that with freshly prepared dimethyldiethoxysilane solutions in ethanol, thismonomer cannot homopolymerize.The next step will be to determine to what extent it can be integrated into the network formed by the polycondensation ofaminoalkylalkoxysilane