New insights on the self-organization of PEG/alpha-cyclodextrin- based Polyrotaxanes in solution: an experimental and theoretical study

Size exclusion chromatography coupled with light scattering (SEC/MALS), dynamic light scattering (DLS), steady-state and time-resolved fluorescence, as well as molecular dynamics (MD) simulations are used to study the behavior of several poly(ethylene glycol) (PEG)/α-cyclodextrins (αCDs) polyrotaxanes (PRs) in solution. The number of CD units in any of the PRs studied is always smaller than that required to saturate the PEG chains. These PRs seem to aggregate in dimethyl sulfoxide (DMSO) solution. The presence of hairpins in the non-saturated PRs contributes to diminishing their expected large dimensions. Intra- and inter­molecular interactions and forces responsible for hairpins and aggregation are investigated.This work was supported by the University of Alcalá (GC2011–002 and UAH2011/EXP-036) and Nanomod (MAT2010–17091) from the Spanish Ministerio de Ciencia e Innovación. The authors acknowledge the assistance of M. L. Heijnen with the preparation of the manuscript