Formation of Side-Chain Hetero-Polypseudorotaxane Composed of α- and β-Cyclodextrins with a Water-Soluble Polymer Bearing Two Recognition Sites

A side-chain hetero-polypseudorotaxane was prepared from a water-soluble polymer (1) bearing heptamethylene (C-7) and azobenzene (Azo) moieties connected with oligo(ethylene glycol) in the side chain by three steps, in which alpha- and beta-cyclodextrins (alpha- and beta-CDs) included the C-7 and cis-Azo moieties, respectively. In the first step, alpha-CD was added to I to form the side-chain polypseudorotaxane, in which alpha-CD included both the C-7 and trans-Azo moieties in the side chain. In the second step, the Azo moiety at the end of the side chain was isomerized to the cis isomer to form the side-chain polyrotaxane, in which alpha-CD was interlocked on the side chain. In the final step, beta-CD was added to the side-chain polyrotaxane to form the side-chain hetero-polypseudorotaxane.