Cucurbit[8]uril‐Based Polymers and Polymer Materials

Abstract

Cucurbit[8]uril (CB[8]) is unique and notable in the cucurbit[n]uril family, since it has a relatively large cavity and thus is able to simultaneously accommodate two guest molecules. Typically, an electron-deficient first guest and an electron-rich second guest can be bound by CB[8] to form a stable 1:1:1 heteroternary supramolecular complex. Additionally, two homo guests can also be strongly dimerized inside the cavity of CB[8] to form a 2:1 homoternary supramolecular complex. During the past decade, by combining polymer science and CB[8] host-guest chemistry, a variety of systems have been established to construct supramolecular polymers with polymer chains typically at the nanoscale/sub-microscale, and CB[8]-based micro/nanostructured polymer materials in the form of polymer networks and hydrogels, microcapsules, micelles, vesicles, and colloidal particles, normally in solution and occasionally on surfaces. This Review summarizes the noncovalent interactions and strategies used for the preparation of CB[8]-based polymers and polymer materials with a focus on the representative and latest developments, followed by a brief discussion of their characterization, properties, and applications.

Photo/redox-responsive 2D-Supramolecular assembly involving Cucurbit[8]uril and a star-shaped porphyrin tecton

“…These studies, and many others [16,[21][22][23][24][25][26][27][28][29], have served to establish that the effective formation of such multi-center bonded dimers in solution actually requires either very low temperatures and/or high concentrations in radicals. As an alternative, viologen-based -dimers can also be observed in standard temperature and concentration ranges, when using barrel-shaped cavitan ds known as cucurbit [8]urils (CB [8]), made of 8 glycoluril moieties connected by methylene bridges, whose inner cavity is ideally suited to the inclusion of two viologen-based radicals [30][31][32][33][34][35]. Such process is illustrated in Figure 1C with a calculated structure of the inclusion complex [(R 1 R 2 ) 2 ] 2+  CB [8] obtained upon mixing CB [8] with two equivalents of N,N′-dimethyl-4,4′-bipyridinium radicals R1VR2 2+ .…”

“…As a matter of facts, the high affinity of CB[n]s (n = 7 or 8) for viologens dications and cation radicals has been extensively used over the past decades to devise a wide range of redox-or chemically-responsive rotaxane-like molecular systems [36,37]. More recently, viologen and cucurbiturils have also been considered as key building blocks in the development of various potentially responsive 2D/3D self-assembled structures [30,35,38,39], the underlying idea being that the dimensionality of the assemblies can be tuned with the number of viologens units available on each tectons.…”

Dual‐Stimuli Responsive 2D Supramolecular Organic Framework for the Detection of Azoreductase Activity

“…As shown in Figure a, the absorption peak at 345 nm in the near‐UV region for the SOF solution decreased, whereas the absorption peak at 432 nm in the visible region increased, showing the rapid transition from trans ‐AZO to cis ‐AZO under UV light (365 nm) within 3 min (Figure S4 in the Supporting Information). It is geometrically unsuitable for the structurally altered AZO to enter the cavity of CB[8], resulting in the disintegration of the 2D SOF. This was further illustrated by SEM (Figure c), which showed the disorderly structure of the SOF after UV irradiation.…”

Oligomeric Cucurbituril Complexes: from Peculiar Assemblies to Emerging Applications

“…[81] An elegant strategy to shift equilibria toward polymers is to use tetratopic (four sites of binding) guests. [33,39,49,58,59,82] Besides "linear" 2:2complexes,bent guests (Figures 8c,12c,13a,14b or 14 e), [60,[73][74][75] lead to rigid but "curved"2:2 complexes which could be useful for the construction of more advanced architectures.This raises the question of the absence of cyclic n:n oligomers,w hen CB [8] is mixed with guests having a q angle between building-blocks different from 1808 8 (Figure 2).…”