Synthesis of linear cucurbit[7]uril pendent copolymers through radical polymerization: Polymers with ultra‐high binding affinity

Abstract

Cucurbiturils (CBs) are a family of macrocyclic molecules with high binding affinity and high binding selectivity. [1][2][3][4][5][6][7] They have been intensively researched for the past decade and have applications in a wide range of fields including molecular recognition, catalysis, drug delivery, bioassays, nanoparticle synthesis and modification, and molecular devices.1-3 Their anchoring onto macromolecules offers further opportunities to expand their applications, [8][9][10] however there are currently few examples of such reports.11-16 The relatively few reports are likely as a result of the difficulties encountered in the modification of CBs; this problem persisted until Kim's group reported the functionalization of CBs with a facile oxidation method in 2003.17 Through oxidization of CBs with persulfate, hydroxyl groups -which are suitable for further functionalization-could be introduced at their peripheries. Following that a series of polymer nanocapsules constructed with perallyloxy-CB[6] and dithiols have been reported. [11][12][13] The eminent binding properties of CB[6] allow these polymer nanocapsules to be decorated easily with targeting and labeling groups through host-guest interactions. Recently, allyl functionalized CB[6] and CB [7] were grafted on to hyaluronate through a thiol-ene click reaction, [14][15][16] and where employed for theranostic systems and tissue engineering applications. In addition of the oxidation method, Isaacs's group developed a different method to synthesize CB derivatives. In their works, CB [6] and CB [7] derivatives were synthesized by the condensation glycoluril hexamer with phthalaldehydes and glycoluril bis(cyclic ethers), respectively.18-20 Despite these, there is still an unmet need for new and facile methods for the construction of CB covalently linked polymers to broaden their portfolio of potential applications.The binding properties of the covalently linked macrocycle polymers are one of the key considerations in their design for specific applications. 21,22 Although their binding properties are usually determined by the binding properties of the macrocycle moieties; the structure of polymers also has a profound and sophisticated effect. Based on the research on polymeric cyclodextrins (CDs), if the CD moieties are spatially isolated, their binding affinity to guest molecules decreases slightly; 23-25 while if they are in close proximity, adjacent two CD moieties may have a cooperation effect and both the binding affinity and binding stoichiometry will be affected. [24][25][26][27][28] To the best of our knowledge, there have been no studies on the binding property of polymeric CBs prior to this work. Here, we present a universal method for the synthesis of linear CB [7] pendent copolymers through free radical polymerization (Scheme 1). The binding properties of the obtained copolymers were studied using turbidity measurement, isothermal titration calorimetry (ITC) and NMR.Free radical polymerization is a universal polymerization method which is suitable f...

Controlled gelation kinetics of cucurbit[7]uril-adamantane cross-linked supramolecular hydrogels with competing guest molecules

“…The CB[7] pendent polymer used in this study was synthesized based on an established method of our group 30 . Generally, A CB[7] based monomer, 4-vinylbenzyloxy CB[7], was synthesized through firstly oxidize CB[7] to obtain mono-hydroxy CB[7] before graft 4-vinylbenzyl group onto the hydroxyl group.…”

“…1 ). Thus we synthesized two N,N -dimethyl acrylamide based polymers with CB[7] and AD pendants 30 . Through pre-saturation the CB[7] pendent polymer with various competing guest molecules and concentrations, the gelation kinetics of the two polymers changes significantly and the gelation time varies from seconds to hours.…”

Modulating the oxidation of cucurbit[n]urils

“…Functionalised derivatives have also been further modified to allow immobilisation onto surfaces 12,14 and attachment to polymeric backbones has been shown by Tan and co-workers. 17 As the isolation of large amounts of pure, open-chain oligomers requires ample synthetic skill, it is not surprising that the oxidative approach of the parent CB[n] homologues has been more widely explored. This method relies upon the formation of OH radicals leading to hydroxylation at the equatorial C-H positions.…”

“…Reported in the synthesis of monofunctionalised CB [6] 11 , a bisimidazolium guest was used to greatly enhance solubility and promote functionalisation. This guest has also been used in the analogous functionalisation of CB [7] by Tan et al 17…”

Synthesis of cucurbit[6]uril pendent upper critical solution temperature type copolymers: self‐assembly and multi‐stimuli‐responsive behavior

“…Free radical polymerization is a universal strategy, applicable to a wide range of monomers and for the synthesis of (co)polymers with versatile functions. Tan and colleagues synthesized CB[7]‐derivatized vinyl monomers, which were then subjected to free radical polymerization 23 . Such covalently linked copolymers of CB[7] displayed multi‐stimuli‐responsive behavior and could be used for the construction of supramolecular materials.…”