Supramolecular Assemblies of Cyclodextrins with Polymers and Preparation of Polyrotaxanes

Cyclodextrins (CDs) have been found to form inclusion complexes with various polymers with high selectivities to give stoichiometric compounds in crystalline states. α-CD formed complexes with poly(ethylene glycol)(PEG) of molecular weight higher than 300, although β-CD did not form complexes with PEG of any molecular weight. However, β-CD formed complexes with poly(propylene glycol)(PPG), although α-CD did not form complexes with PPG of any molecular weight. γ-CD formed complexes with poly(methyl vinyl ether)(PMVE), though α- and β-CD did not form complexes with PMVE. Polyrotaxanes in which many CDs are threaded on a single PEG chain were prepared by capping the chain ends of the complex with bulky groups. The neighboring CDs in a polyrotaxane are crosslinked by epichlorohydrin and then stoppers at the both ends and the polymer chain of the crosslinked polyrotaxane were removed by strong base to give a tubular polymer, a molecular tube.