A one-step synthesis of polyrotaxane via in situ Michael addition reaction

A kind of one-step synthesis of polyrotaxane (PR) was achieved via in situ Michael addition reaction. The acrylate terminated poly(ethylene glycol) (a-PEG) was initially synthesized. Then, the PR was synthesized in situ with a novel stopper mono-thiolated β-cyclodextrin (SH-β-CD) via Michael addition reaction. A pseudo-polyrotaxane (PPR) was formed in water by a-PEG and α-CDs. This strategy was not only able to prevent the de-threading of CDs, simplify the PR’s synthetic procedure, and achieve high yield but also obtained biocompatible and environment-friendly PRs. Furthermore, the influence of reaction conditions on the yield and CD coverage ratio were thoroughly investigated. It showed that the yield increased with increasing solubility of SH-β-CD, resulting from the introduction of DMF, while the CD coverage ratio almost was kept as a constant with the change in feed ratio of α-CD. The highest yield of around 29 % was obtained by this method, whereas a relative high CD coverage ratio of around 60 % was achieved simultaneously. This result showed a promising potential in the large scale PR production. Finally, the successful preparation and the structure of the resulting PR were confirmed by IR, NMR, and DSC. The GPC traces exhibited a narrow molecular weight distribution, and the XRD confirmed the PR’s channel-type structure.