Macromolecular recognition: new cyclodextrin polyrotaxanes and molecular tubes

It was found that cyclodextrins (CDs, α-, β- and γ-CD) formed inclusion complexes not only with hydrophilic polymers, such as poly (ethylene glycol) (PEG), poly (propylene glycol) (PPG) and poly (methyl vinyl ether) (PMVE), but also with hydrophobic polymers, such as oligoethylene, polypropylene, polyisobutylene and polyesters. α-CD formed complexes with oligoethylene, although β- and γ-CD did not under the same conditions. γ-CD formed complexes with polyisobutylene in high yield, although α-CD did not. There is a good correlation between the sizes of cavities of cyclodextrins and the cross-sectional areas of the polymers. The polymer complexes are crystalline and polyrotaxane-type inclusion complexes. It was also found that cationic polymers such as viologen polymers and polyionenes form complexes with cyclodextrins to give soluble complexes in water. New polyrotaxanes in which many CDs are threaded on to polymer chains have been prepared by capping both polymer ends by large stoppers.