Regulation of pseudo-Polyrotaxane Formation between α-Cyclodextrins and Azobenzene-Terminated Poly(ethylene glycol)


Regulation of pseudo-polyrotaxane formation between α-cyclodextrins (α-CDs) and azobenzene(Az)-terminated poly(ethylene glycol) (PEG) was studied in terms of the photoisomerization of the terminal Az groups. pseudo-Polyrotaxane formation was analyzed by a change in the transmittance at 550 nm in water. It was found that the rate of transmittance change was decreased with an increase in the cis isomer content in Az-PEG. The cis-isomerization effect was quantitatively evaluated, assuming that Az-PEG having two cis-isomerized Az groups does not participate in the pseudo-polyrotaxane formation. From this analysis, it is suggested that pseudo-polyrotaxane formation between α-CDs and PEG was hindered when the both terminal Az groups were isomerized to cis isomer. The content of Az-PEG in the pseudo-polyrotaxane aggregate and the content of cis-isomerized Az-PEG in the supernatant were measured by 1H NMR and UV-Vis absorption spectrum, respectively, and the obtained results supported our suggestion. It is concluded that the terminal Az groups act as a gate to regulate the pseudo-polyrotaxane formation.


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Ikeda, T., Ooya, T. & Yui, N. Regulation of pseudo-Polyrotaxane Formation between α-Cyclodextrins and Azobenzene-Terminated Poly(ethylene glycol). Polym J 31, 658–663 (1999).

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  • pseudo-Polyrotaxane Formation
  • Photoisomerization
  • α-Cyclodextrin
  • Poly(ethylene glycol)
  • Azobenzene

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