Preparation of Polyrotaxanes and Molecular Tubes for Host-Guest Systems

Linear polymers, such as long chain aliphatic alcohols or polyethyleneoxide derivatives, can form peculiar structures (called "polyrotaxanes"), when mixed with molecules that contain a suitable cavity, for example cyclodextrins and crowns. Polyrotaxanes can be converted into stable structures called "molecular necklaces" and "molecular tubes", that keep the hosting properties of their precursors, and that can be used to entrap small molecule or ions in their cavities. These products are relevant in the study of several biological structures (ribosomes, membranes, DNA complexes), and for the development of industrial processes in which the main factor is the uptake and removal of an undesired product, or its transfer from one environment to another medium. We report some studies carried out by kinetics, UV and NMR measurements on the structure and properties of some cyclodextrin based host molecules, and their capacity to include ions or small molecules.