PROPERTIES AND STRUCTURE OF AQUEOUS-SOLUTIONS OF HYDROXYPROPYL-BETA-CYCLODEXTRIN

Molecules of hydroxypropyl-beta-cyclodextrin (HPBCD) in aqueous soluti on interact with each other via hydrogen bonds. Especially for concent rations beyond 50% (w/w), a strong increase in viscosity and a conside rable decrease of freezable water can be determined. The addition of s ubstances which are able to break the water structure (urea, KSCN) red uces these effects remarkably. The formation of inclusion compounds wi th urea could not be detected. Endothermic phase transformations confi rm the presence of liquid crystalline structures at low temperatures. These liquid crystalline structures are not detectable at room tempera ture, but the freeze fracture technique shows micelle-like associates of a size of about 20 nm. Studies on the complexation of phenolphthale in as well as surface tension measurements of HPBCD solutions indicate that a minimum concentration of HPBC is necessary for the association phenomena.