Biobased thermosensitive polyrotaxanes constructed by polymerization of cyclodextrin-triterpenoid inclusion complexes†
In this work, three cyclodextrin-based polyrotaxanes (CD-based PRs) with alternating multiblock structures were constructed by polymerization of inclusion complexes in a convenient tandem way, where an inclusion complex of a natural glycyrrhetinic acid (GA) derivative and γ-CD polymerized with three PEG-dicarbonates, respectively, followed by capping with amino-β-CD. During the formation of CD-based PRs, only a small amount of γ-CD slipped off and around 90% of GA units on the guest polymer were complexed with γ-CD. Note that although the three CD-based PRs had similar molecular weights of ∼50 000 Da, the decrease of the PEG length (from 4000 to 600 Da) led to an enhancement of the structural rigidity and the variation in the hydrophilic–lipophilic balance (HLB). In this case, the sizes of the assembled spherical micelles and the reversible phase transition behaviors were effectively regulated by the molecular rigidity and HLB. Our biocompatible CD-based PRs with precise controllable performance may lead to further exploration of thermosensitive materials.