pH-Controllable cyclic threading/dethreading of polypseudorotaxane obtained from cyclodextrins and poly(amino ester)

Cyclic threading/dethreading of novel polypseudorotaxane obtained from β-cyclodextrins and poly(amino ester), poly(BDA-DEEDA), obtained from the Michael addition polymerization of 1,4-butanediol diacrylate (BDA) and N, N′-diethyl ethylenediamine (DEEDA), was realized by adjusting pH of the aqueous solutions between ca. 9.0 and 3.2 alternatively. 1H NMR, XRD profiles, and 13C CP/MAS NMR verified the formation of polypseudorotaxane, and acid titration induced dethreaded structures were characterized using 2D ROESY NMR, 1H NMR and XRD. The appearance/disappearance of precipitates, the kinetics, and the cyclic performance of pH controllable threading/dethreading processes were monitored by the changes in absorbance or transmittance of the solutions as reflected by UV experiments. Further pH-induced protonated and deprotonated states of poly(BDA-DEEDA) were demonstrated by 1H NMR, which indicated the mechanism of the threading/dethreading processes.