Graftpolyrotaxane: Graft polymer possessing movable graft chains on cyclodextrins as the polyrotaxane wheels

Graftpolyrotaxanes having graft chains on the wheel components were prepared from main chain-type polyrotaxane having monofunctional cyclodextrin wheels and terminal end-reactive poly(ethylene glycol) (PEG). The well-defined polyrotaxane having mono(6-hydroxyl) permethyl-α-CD (monoOH-α-CD) as the wheel components and a polytetrahydrofuran (PTHF) axle with bulky end-capping groups was synthesized by the two pathways; (i) synthesis by solid-state end-capping of pseudopolyrotaxane consisting of monoOAc-α-CD and hydroxy-terminated PTHF and (ii) one-pot synthesis using monoOH-α-CD and amine-terminated PTHF in water. The grafting reaction on the wheel moieties of the resulting polyrotaxane was carried out by acylation reaction with PEG-mono-carboxylic acid derivatives in high conversion yields. To estimate the relative rotary movement of CDs and the axle polymer in the polyrotaxane and graftpolyrotaxane, the rotational correlation time (τc) of polyrotaxanes was estimated from the longitudinal relaxation time (T1) of 13C NMR. The results clearly indicate that the graftpolyrotaxane described here is a new type of graft polymer in terms of the special circumrotation behavior such as the independent rotary movement of CDs with the graft chain and the axle polymer.