ICMUB - News

Vendredi 29 février 2008 : Conf de Gerhard Wenz, Sarrebruck (Allemagne)

Supramolecular chemistry of cyclodextrins and polymers

Cyclodextrins are doughnut-shaped cyclic oligomers of amylose consisting of 6, 7 or 8 glucose units called -, - or γ-CDs, respectively. Cyclodextrins spontaneously thread onto many linear polymers, such as polyethers, polyesters or polysiloxanes in aqueous media due to hydrophobic interactions. The resulting pseudo-polyrotaxanes are generally insoluble in water, since the CD rings are tightly packed linearly along the polymer chain forming so-called channel inclusion compounds. Threading is sterically controlled by the diameters of the polymer chain and the CD cavity.
On the other hand, highly water-soluble ionic polymers with sufficiently long hydrophobic spacer groups, so-called poly(bola-amphiphiles) allow threading under homogenous conditions in aqueous solution. CD rings are separated by the ionic groups which also control the rates of threading and dissociation.
Rotaxanation of polymers can lead to improved solubilities in water, as shown recently for poly(phenylene-vinylene) PPV polyrotaxanes. In addition, the chemical stability of a polymer can be dramatically increased by the shielding effect excerted by the CD rings. So-called molecular wires could be created.
Pseudopolyrotaxanes can be used as supramolecular entities showing a programmable lifetime, which should be very useful for medical applications. Polyfunctional pseudopolyrotaxanes equipped with specific ligands, such as sugars, might be applicable for the targeted delivery of drugs, especially for cancer therapy. Compared to conventional polymeric carriers they offer several advantages, such as modular assembly from well-defined building blocks and tuneable lifetimes.

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Contact : Jean-Claude Chambron

ICMUB (UMR 5260) - University of Burgundy - Dijon (France)