One-Pot Synthesis of Native and Permethylated α-Cyclodextrin-Containing Polyrotaxanes in Water

Abstract

Efficient one-pot synthesis in water of polyrotaxanes, with native and permethylated α-cyclodextrins (α-CD and PMe α-CD) as the wheel components, is described. The procedure involves initial mixing of α-CDs and an amine-terminated linear polymer, which acts as the axle, by sonication and subsequent addition of an end-capping agent for the axle terminal amino groups. The polyrotaxanes were prepared by mixing the axle and wheel components by sonication for 30 min at room temperature and standing overnight if necessary, followed by treatment with a bulky isocyanate in water at 0 °C for an hour. Both amine-terminated polytetrahydrofuran (ATPT) and poly(ethylene glycol) (ATPEG) afforded the corresponding polyrotaxanes (PRXs) in good yields (27−49%) in the case of a native α-CD wheel. The coverage ratio of the axle component with the wheel component of the PRXs ranged from 85% to 96% when the molecular weight of the axle was Mn 1000−1800, while it was 54% when the axle was long (Mn 7700). The polyrotaxanes (PMePRXs) with PMe α-CD and ATPT were similarly obtained in high yields. In this case, the yield of the PMePRXs was unusually high (66 and 69%) when a higher molecular weight axle (Mn 4100 and 7100, respectively) was used. The formation of a PMePRX from ATPEG axle proceeded with low efficiency. The present work provides the first synthesis of polyrotaxanes with PMe α-CD in solution.