High yield production of high molecular weight poly(ethylene glycol)/α-cyclodextrin polyrotaxanes by aqueous one-pot approach

An easy, one-pot, high-yield preparation of high molecular weight polyrotaxanes (PRs) from poly(ethylene glycol) (PEG) and α-cyclodextrin (α-CD) by click chemistry is presented with novel water soluble and clickable end-capping agents containing quaternary ammonium and propargyl groups. The threading numbers of α-CD on the PEG chain were investigated by means of 1H NMR spectroscopy and gel permeation chromatography (GPC). When Mn of the PEG axis is 35 kDa, the yield is up to 614 mg per 100 mg PEG axis and the average number of α-CDs on each PEG axis is 193. Wide-angle X-ray diffraction (WAXD) revealed that PRs form a column-type crystalline structure. The prepared PR possesses terminal alkyne groups which can connect with functional molecules to make the PR more useful. As a typical example, fluorescent rhodamine B has been successfully installed on the PR terminals.