Synthesis And Properties Of (Poly)Pseudorotaxanes With Cucurbituril As Host Molecule

Supramolecular chemistry has ushered polymer chemistry into a new era. In supramolecular chemistry,(pseudo)polyrotaxanes, in which many cyclic molecular 'beads'are threaded by a long'string', have received much attention in recent years not only because of their unique structures but also because of their unusual properties different from those of conventional covalent polymers, such as potential use as a material for molecular devices and catalyst. Since the earliest example of poly (ethylene glycol) containing a-cyclodextrin threaded in aqueous media, α-,β-and y-cyclodextrin, crownether, and cyclophane have been threaded onto a number of different linear polymer backbones.Cucurbit[n]uril (CB[n], n=5-10) is a family of macrocylic compounds comprising n glycoluril units. The defining features of CB[n] are their two portals lined by ureido carbonyl groups that provide entry to their hydrophobic cavity. CB[6] has a cavity of5.5A" Diameter, that allow CB[6] to form stable host-guest complexes with small molecular such as butyl ammonium ion. CB[7], a water soluble, barrel-shaped host, consists of7glycoluril groups and14methylene bridges at both ends. The two rims are formed by the glycoluril carbonyl oxygen, thereby are negatively charged, and they develop ion-dipole interactions with cationic guests.1. Novel supramolcular hydrogels with CB[6] induced were prepared. The experimental result indicated that the salt of butan-1-aminium4-methylbenzenesulfonate (BAMB) and CB[6] could form hydrogels, whereas neither BAMB nor CB[6] alone could self-assemble into supramolecular hydrogels. The study of the gelation confirmed that the hydrogels was sensitive to the temperature, and the gel-sol transition temperature rose with increasing the concentration of either BMAB or CB[6], as well it was found that the mixtures aggregate into fibers, which leaded to the formation of three-dimensional network by combination of multiple interactions such as hydrophobic interaction,π-π stacking interaction, van der walls interaction.2. Novel water soluble side-chain pseudopolyrotaxane with CB[7] were synthesized, and CB[7] was localized on the viologen units in side chains of the polymer. The experiment results indicated that the average size of the aggregates in water increased with the increasing of CB[7] threaded as found by DLS and, and the regularity of the polymer chain conformation increased with increasing amount of CB[7] threaded, which led to the increasing of the polymer thermal stability. The typical cyclic voltammograms showed that the peak potentials had a noticeable shift and the peak areas had a marked decrease with increasing the mole ratio of CB[7] threaded.3. Novel water soluble side-chain pseudopolyrotaxane with CB[7] were synthesized, and CB[7] could move by adjusting the molar ratio of CB[7] to the monomer4VBVHeP. When the molar ratio of CB[7] to4VBVHeP is equal to1, CB[7] were threaded onto the hexyl unites of the side chains of P4VBVHeP, and CB[7] could be shoved onto the benzyl and a part of viologen unites of the side chains. The slippage of CB[7] by adjusting the molar ratio of CB[7] to4VBVHeP was characterized by1H NMR and cyclic voltammograms. Meanwhile, the typical cyclic voltammograms showed noticeable shifts in the peak potentials and a marked decrease in the current levels with increasing the molar ratio of CB[7] to4VBVHeP. Both DLS and RLS results showed that the average sizes of the polypseudorotaxanes in water increased with the increase of the molar ratio of CB[7] to4VBVHeP, and UV-vis data showed that CB[7] are not threaded in the viologen units of polymer P4VBVHeP, which is the indirect evidence of the slippage of CB[7] onto the side chains of polymer.4. The aggregation behaviors of PMAA with CB[7] in aqueous solution were investigated. The experiment data show that CB[7] could combine with H+of PMAA in aqueous solution, which lead to the formation of the aggregates. And the size of the aggregates increases with increasing the concentration of CB[7] because that the transition between the intrachain and interchain association appear with adding CB[7], when the two COO-and one+HCB[7]H+can driven together to form complex point. Moreover, PMAA has temperature sensitivity with the addition of CB[7] by UV-spectrophotometer and DLS, and pH of the solution of PMAA appears a inflection point with increasing the concentration of CB[7] due to the formation of+HCB[7]H+With the addition of the dilute ammonia into PMAA, CB[7] could combine with NH4+by the electrostatic and iondipole interactions, and the size of the aggregates also increases with increasing the concentration of CB[7]. And on the basis of all data, a schematic representation for the different binding regions and the behaviors of the aggregation is proposed.5. Non-toxic star polypseudorotaxanes were synthesized by a simple method, and the bactericidal activity of the star polypseudorotaxanes was studied by adjusting CB[7] unthreaded with the addition of another competitive guest ADA. We demonstrated the use of synthetic polypseudorotaxanes to provide triggered activation of a therapeutic by competitive complexation. The experiment results indicate that the viologen unites of polypseudorotaxanes could fall off from the hydrophobic cavity of CB[7] with adding ADA and the star polypseudorotaxanes have the redox property with adding ADA comparing with the non-redox properties of the polypseudorotaxanes without adding ADA. At the same time, the bactericidal activity experiment of polypseudorotaxanes with adding ADA indicates that ADA acts as an effective trigger for the competitive release of CB[7] from viologen unites within the cell, with attendant activation of cytotoxicity.