Cucurbit[7]uril moving on side chains of polypseudorotaxanes: Synthesis, characterization, and properties

Abstract

Novel side chain polypseudorotaxanes with cucurbit [7]uril (CB[7]) threaded onto the side chains are synthesized from a water-soluble polymer and CB [7] in water by simple stirring at room temperature. CB [7] beads could move from the hexyl groups to the benzyl and a part of viologen units in the side chains of polymer when the molar ratio of CB[7] to the monomer reaches from 1 to 2 as shown by 1 H NMR studies, and it is considered that the hydrophobic and charge-dipole interactions of CB [7] are the driving forces. The sizes of the polypseudorotaxanes with different molar ratio of CB[7] to 4VBVHeP in aqueous solution increase with increasing the molar ratio of CB[7] to 4VBVHeP as found by DLS and resonance light scattering, while the typical cyclic voltammograms and UV-vis data indicate that CB [7] are not threaded in the viologen units of P4VBVHeP, and the oxidation reduction characteristic of the polymer is remarkably affected by the addition of CB[7]. Cucurbit[7]uril (CB[7]), a water-soluble, barrel-shaped host, consists of 7 glycoluril groups and 14 methylene 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. 28,29 Recently, taking advantage of cucurbit[7]uril's structure, various mechanically interlocked molecules including rotaxanes and poly(pseudo)rotaxanes have been synthesized by Kim, [30][31][32][33][34][35][36][37][38][39] Kaifer, 40-42 and others. [43][44][45][46][47][48][49][50][51][52][53][54][55][56] We previously synthesized some side chain polypseudorotaxanes with viologen, and cucurbit[7]uril as a molecular bead have also been reported. 52This investigation expends our understanding about the movement on the side chains of polypseudorotaxanes. Herein, we synthesized novel water-soluble side chain polypseudoro-taxanes with CB[7], which could slippage on the side chains by adjusting the molar ratio of CB[7] to the monomer. The weight-average molar mass M w of the polymer was measured by multiangle laser light scattering, and the movement of CB[7] on the side chains of polypseudorotaxanes by adjusting the molar ratio of CB[7] to the monomer were studied by 1 H NMR. The average hydrodynamic radius (R h ), the oxidation reduction characteristics, and optical properties of the polypseudorotaxanes were studied by DLS, cyclic voltammograms, UV-vis, and resonance light scattering (RLS), respectively. CB[7] was prepared according to the literature. 29,30 4,4 0 -Dipyridyl (98%), pyridine (99%), 1,6-dibromohexane (99%), and 4-vinybenzyl chlorine (90%) were received from ACRO. Anhydrous acetonitrile (AR) and diethyl ether anhydrous (AR) were received from the Sinopharm Chemical Reagent (SCRC). EXPERIMENTAL MaterialSynthesis of 1-(6-Bromohexyl)pyridinium (HeP) 1,6-Dibromohexane (18.3 g, 0.075 mol) was dissolved in absolute ether (25 mL) and stirred for 10 min at room temperature. Pyridine (2.0 g, 0.025 mol) was slowly dripped to the solution of 1,6-dibromohexane, and the mixture was

Radical‐Cation Dimerization Overwhelms Inclusion in [n]Pseudorotaxanes

“…The signals of both β and β′ aromatic protons experience a small downfield shift. Together, these results are consistent with complexation of the benzyl ring by CB7 through hydrophobic and dipole–charge attractions, and with interaction (see Supporting Information) between C B7 and only part of the viologen moiety 70–71…”

“…Together, these results are consistent with complexation of the benzyl ring by CB7 through hy- drophobic and dipole-charge attractions, and with interaction (see Supporting Information) between CB7 and only part of the viologen moiety. [70][71] The binding of BMV 2 + by CB7 was also examined by absorption spectrophotometry (see Supporting Information). Unlike recognition of MV 2 + by CB7, the recognition of BMV 2 + by CB7 has little influence on the BIPY 2 + p-p transitions, which indicates, as do the 1 H NMR data, that the CB7 host does not fully encircle this chromophore but is instead positioned on the benzyl moiety.…”

Dynamic supramolecular polymers built from cucurbit[n]urils and viologens

“…2(b)). 49,50 With CB [8], the large size of the inner cavity enables a wide range of -conjugated donor-acceptor pairs to be stabilized. This specific feature has been exploited to develop the different elongation approaches sketched in Fig.…”

Self‐Protection of Electrochemical Storage Devices via a Thermal Reversible Sol–Gel Transition

“…In addition, the average molecular weight of the copolymer and degree of polymer were determined using multiage laser light scattering (Wyatt Technology DAWN HELEOS 18 angle light scattering) in aqueous solution. Static light‐scattering data show the average molecular weight of PNIPAM/AM is 3.68 × 10 6 g mol −1 and the distribution of polymer is 2.95 as shown in Figure S8 (Supporting Information) . The transition temperature of sol–gel process of copolymers was carried out using a HITACHI U‐3010 spectrophotometer.…”