PH-Responsive polypseudorotaxane synthesized through cucurbit[6]uril catalyzed 1,3-dipolar cycloaddition

A pH-responsive polypseudorotaxane has been synthesized via cucurbit[6]uril (CB6)-catalyzed 1,3-dipolar cycloaddition using diazide and dialkyne monomers, which contain a long aliphatic-spacer. The polypseudorotaxane was characterized by spectroscopic techniques (H-1, C-13 NMR and FT-IR) and matrix assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS). The experimental results reveal that this polypseudorotaxane behaves as a pH-driven polymeric switch. Thus, when amine groups are protonated at an appropriate pH, CB6s are located on the triazole rings due to ion-dipole interaction, whereas at high pH they move onto the hydrophobic aliphatic spacer rather than slipping off the polypseudorotaxane.