More on Polypseudorotaxanes Formed between Poly(ethylene glycol) and α-Cyclodextrin

A new interpretation for the mechanism associated with the spontaneous threading of alpha-CD, onto a PEG chain followed by the supramolecular hydrogel formation, is described. Beyond a specific stoichiometry, the complexation of alpha-CD and PEG results in the formation of a two-phase system. Besides the phase separation, for PEG with a molecular weight higher than 6000 Da, part of the polymer chains are unthreaded by the alpha-CD, leading to the formation of a supramolecular hydrogel. The kinetics for the complexation and the determination of the yield for equilibrated systems consisting of PEG (linear and star) are used to investigate the number of alpha-CD threaded before and after the phase separation. The results are compared with the prediction obtained from the application of the Poisson distribution and reveal the ratio between alpha-CD and PEG in each step of the process. Additionally, the kinetics for the hydrogel formation and its inner structure are investigated by using the proton NMR spin-spin relaxation of water.