α,ω-Dimesyl-terminated poly(ethylene glycol) (PEG-Ms2) and α,ω-ditosyl-terminated PEG (PEG-Ts2) were prepared from PEG (PEG
1000;
Mn=1000 and PEG
4000;
Mn=4000) and methanesulfonyl chloride or
p-toluenesulfonyl chloride. α,ω-Ditosyl-terminated PEG
4000 pseudorotaxane (PEG
4000-TS2-
pseudorotaxa-α-cyclodextrin (α-CD) was prepared from PEG
4000-TS2 and α-CD in H
2O. (
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 PEG
4000-BINOL2-
rotaxa-α-CD was isolated in 38% yield. For a PEG
4000-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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