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Véronique Wintgens

Publications and source records attributed to Véronique Wintgens.

5 recordsLinked to original sources
PubMed2006

Macromolecular assemblies based on coupled inclusion complex and electrostatic interactions.

Macromolecular assemblies are elaborated by mixing beta-cyclodextrin-containing polymer (polybetaCD), dextran sulfate polyanion (NaDxS), and cationic amphiphiles which are adamantane derivatives (Ada1 or Ada2) in aqueous medium. These components are assembled via coupled inclusion complex interactions (adamantyl group with cyclodextrin cavity) and electrostatic attractive interactions (positive charges of Ada with negative charge of NaDxS). The structural properties are studied by viscometry and small angle neutron scattering. Ternary aggregates with larger size and lower compacities are observed as the cation concentration is increased, until phase separation occurs. The results are in good agreement with a core-shell association mechanism, the core being made of one polybetaCD chain, the shell of NaDxS chains, and the Ada amphiphiles being distributed more or less homogeneously inside the cyclodextrin cavities. The nature of the Ada counterions has a strong influence on the association as Ada1 with I(-) counterions give smaller and less compact aggregates than Ada2 with Br(-) counterions.

Binding, Competitive↗
PubMed2005

Polymeric micelles and nanoparticles from block and statistical poly((RS)-3,3-dimethylmalic acid) derivatives: preparation and characterization.

Amphiphilic and biodegradable micelles and nanoparticles designed as potential drug carriers were prepared from biodegradable statistical and block copolyesters obtained by a living anionic ring-opening process. These novel materials display amphiphilic properties arising from the joint presence of hydrophilic poly((RS)-3,3-dimethylmalic acid) and hydrophobic poly(hexyl (RS)-3,3-dimethylmalate) segments. Micelles obtained from a well-defined block copolymer have been characterized by their critical aggregation concentration, and nanoparticles derived from statistical copolymer have been analyzed by transmission electron microscopy (TEM).

Drug Carriers↗
PubMed2005

Associative pH sensitive system.

New associative pH sensitive systems composed of a modified dextran bearing 2-carboxycyclohexyl carboxyl groups and neutral (p betaCD) or positively charged (p betaCDN(+))beta-cyclodextrin-co-epichlorhydrin copolymers have been synthesized and their properties were investigated as a function of pH by phase diagrams and viscosimetry. The affinity between the CD cavities and the hydrophobic guests (2-carboxycyclohexyl carboxyl groups) has been studied as a function of pH. The system with the neutral p betaCD shows a pH dependent behavior due to the lowest affinity of the guest at pH above 5 for the cavity. Associative phase separation is produced at low pH whereas soluble complexes occur at higher pH. The opposite trend is observed with the system containing the cationic p betaCDN(+). This behavior is due to the combination of electrostatic and inclusion complex interactions in this system. Addition of salt, by screening the electrostatic interactions, also strongly influences the response of the system.

Dextrans↗
PubMed2003

Solvent and temperature effects on the deactivation pathways of excited ion pairs produced via photoinduced proton transfer.

The kinetics of the energy dissipation pathways of the excited ion pairs formed upon light absorption of the hydrogen bonded complex between N-methyl-3-hydroxynaphthalimide (3HONI) and 1-methyl-imidazole (MIm) has been studied in a wide temperature range in solvents of various polarities. In polar media such as butyronitrile, three emitting species are found which are assigned as hydrogen bonded, solvent separated and free ion pairs. In contrast, less polar solvents do not favour free ion pair formation, and reversible transition occurs between the excited hydrogen bonded (HBIP) and solvent separated (SSIP) ion pairs around room temperature. Systematic steady-state and time-resolved fluorescence measurements combined with computer modelling enabled the deduction of the kinetic parameters for all excited state deactivation processes in solvents of moderate polarity. The Arrhenius parameters of the interconversion between the ion pairs, the A-factor for the radiationless deactivation of SSIP and the radiative rate constant of HBIP diminish with the increasing dielectric constant of the media. The enthalpy and the entropy change in the SSIP formation from HBIP become less negative in more polar solvents. Going from ethyl acetate to CH2Cl2 the most profound decrease (more than three orders of magnitude) is observed for the A-factor of SSIP --> HBIP reaction.

Journal Article↗