Abstract
α,ω-Dimesyl-terminated poly(ethylene glycol) (PEG-Ms2) and α,ω-ditosyl-terminated PEG (PEG-Ts2) were prepared from PEG (PEG1000; Mn=1000 and PEG4000; Mn=4000) and methanesulfonyl chloride or p-toluenesulfonyl chloride. α,ω-Ditosyl-terminated PEG4000 pseudorotaxane (PEG4000-TS2-pseudorotaxa-α-cyclodextrin (α-CD) was prepared from PEG4000-TS2 and α-CD in H2O. (S)-(-)-1,1′-Bi(2-naphthol) ((S)-BINOL) was added to the pseudorotaxanes in the presence of sodium hydride to give PEG-rotaxa-α-CDs end-capping (S)-BINOL (PEG-BINOL2-rotaxa-α-CD). The purified PEG4000-BINOL2-rotaxa-α-CD was isolated in 38% yield. For a PEG4000-TS2, the average number of α-CD's per chain is 29, which corresponds to 64% coverage. After end-capping reaction, the average number of α-CD's per chain is 14, which corresponds to 31% coverage. The threading level in the polyrotaxane is limited by the coverage of the polypseudorotaxane and by the competition between the end blocking reaction and dethreading. In DMF a rapid dethreading occurs.
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