|dc.description.abstract||In this study, a series of mechanically interlocked molecules like
polypseudorotaxanes, rotaxanes and pseudorotaxanes have been synthesized via CB6
catalyzed 1,3-dipolar cycloaddition using diazide and dialkyne monomers, which
contain long dodecyl and short propyl aliphatic spacers.
To reach these novel interlocked molecules, first appropriate monomeric units were
designed and synthesized. These monomeric units were diazido and dialkyne
functionalized, propyl and dodecyl spacers containing, diamine salts. These
monomers were fully characterized by spectroscopic techniques like 1H, 13C-NMR
and FT-IR and elemental analysis.
After the preparation of the monomers, polypseudorotaxanes were synthesized via
CB6 catalyzed 1,3-dipolar cycloaddition. The polymer formation proceeded through
step-growth polymerization in the presence of CB6. The reaction was followed by
1H-NMR spectroscopy easily, because the appearance of a diagnostic peak at 6.5
ppm indicated the formation of triazole ring, which joins the monomers.
The polypseudorotaxane was also characterized by spectroscopic techniques like 1H,
13C-NMR and FT-IR and matrix assisted laser desorption time-of-flight mass
spectrometry (MALDI-TOF MS). It produced a maximum mass at around 15600 Da which corresponds to about six repeating units that is basically 12 CB6s threaded
triazoles. 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.
After the synthesis of the polypseudorotaxanes, a series of rotaxanes and
pseudorotaxanes have also been synthesized using the already prepared dialkyne and
diazide monomers. Rotaxanation was also carried out via a 1, 3-dipolar cycloaddition
reaction catalyzed by CB6. Among them, a bistable CB6-based rotaxane
synthesized through CB6 catalyzed 1,3-dipolar cycloaddition contains two
recognition sites and behaves as a reversible molecular switch. It exhibits
conformational changes caused by the movement of rings under base, acid and heat
stimuli from one location to the other.||en_US