Direct Synthesis of Cyclodextrin-Rotaxanated Poly(ethylene glycol)s and Their Self-Diffusion Behavior in Dilute Solution

Poly[(ethylene glycol)-rotaxa-(α-cyclodextrin)]s, (PEG-rotaxa-αCD)s, were prepared by a direct route from commercially available poly(ethylene glycol)s (PEG) with molecular weights from 1.5 to 20 kg/mol. The rotaxanated structure was verified by diffusion-ordered 2D NMR spectroscopy (DOSY). The self-diffusion coefficients for PEG-rotaxa-αCD and PEG in dilute DMSO-d6 scale with their respective molecular weights as DPEG-rotaxa-αCD ∼ Mn-0.60±0.05 and DPEG ∼ Mn-0.55±0.03. With increasing temperature, the hydrodynamic radius of the PEG-rotaxa-αCD increases by the same slope as the unthreaded PEG backbone. These polyrotaxanes, in which up to 70% of the backbone is covered with cyclodextrins, behave as random coils in good solvents.