Inclusion complex formed between star-poly(ethylene glycol) and cyclodextrins

Aqueous solutions of alpha- and gamma-cyclodextrins can form spontaneous inclusion complexes with poly(ethylene glycol), PEG, in which the hydrophobic cavities of the cyclic oligosaccharides can be threaded onto the polymer chain. Linear or multiarm PEGs with low molecular weight can be decorated with cyclodextrins, yielding crystalline phases. In this work, we report for the first time the complexation of cyclodextrin with star-poly(ethylene glycol), s-PEG, with high molecular weight, containing 13 and 15 arms. The final result of the complexation is a hydrogel. The kinetics of gelation is strongly affected by the size of the cyclodextrin cavity. The effects of the polymer molecular weight and number of arms on the yield of the complexation and on the gel structure are discussed.