Multiblock copolymer behaviour of alpha-CD/PEO-based polyrotaxanes: towards nano-cylinder self-organization of alpha-CDs

The present work demonstrates that alpha-cyclodextrin/poly(ethylene oxide) (alpha-CD/PEO)-based polyrotaxanes (PRs) behave as multiblock copolymers. One block type consists of a rod-like tube made of 6 to 7 weakly stacked alpha-CDs threaded along the PEO chain. The other one is made of a naked PEO segment, i.e. the PR part that is not covered by alpha-CDs. This multiblock behaviour induces the self-organization of PRs in concentrated solution in dimethyl sulfoxide ( DMSO) at room temperature leading to the formation of nano-cylinders. These nano-cylinders consist of assemblies of roughly 60 alpha-CD rod-like tubes through hydrogen bonding. Moreover, crystallites of naked PEO segments are formed since PEO is in poor solvent conditions ( DMSO) at room temperature. Furthermore, the formation of alpha-CD nano-cylinders as well as of naked PEO segment crystallites leads to physical gelation of PRs in DMSO.