Crown Ether‐Based Polymeric Rotaxanes

Engineering membranes with macrocycles for precise molecular separations

“…Crown ethers, the first generation of synthetic macrocyclic hosts, have been widely utilized to fabricate various supramolecular architectures 39,40 and received a huge interest as complexing agents since the fortuitous discovery by Pedersen in 1967. 41 Pedersen also demonstrated the ability of this class of molecules to bind other alkali metal ions and an ammonium, as extensively reviewed in literature.…”

Supramolecular Four-Armed Star A2B2 Copolymer (Miktoarm Star) via Host–Guest Complexation and Nitroxide-Mediated Radical Polymerization

“…Supramolecular chemistry mainly is concerned with molecular recognition, molecular devices, and self-processing by self-assembly. − The formation of pseudorotaxanes and rotaxanes is a key subject in supramolecular chemistry, which has been expanded to analogous polymeric materials because of their unique properties. − The convergence of the two areas has led to construction of analogues of traditional polymeric structures and architectures using supramolecular methods. Some previously reported examples of macromolecules formed by the self-assembly of pseudorotaxane and rotaxane host and guest units include linear polymers from self-organization of well-defined monomeric building blocks, − dendrimers from cooperative complexation of a homotritopic guest and complementary monotopic dendron hosts, dendrimers from self-assembly, − physically interlocked hyperbranched polymers, − a triarm star polymer from a homotritopic host and a complementary monotopic paraquat-terminated polystyrene guest, polymers with terminal pseudorotaxane units from polymers end-functionalized with crown ethers interacting with small guest molecules, supramolecular diblock copolymers from end-functionalized polymeric building blocks, , and a pseudorotaxane graft copolymer from a main-chain crown polyester and a paraquat-terminated polystyrene guest …”

Rotaxanation of Polyisoprene to Render it Soluble in Water

“…In main chain polyrotaxanes, the macrocycle is threaded on the polymeric backbone, and the dissociation of the constituents is prevented by bulky groups, which are attached at the chain ends or randomly along the chain. , Side chain polyrotaxanes possess rotaxanated units that are positioned at side groups of the polymer . Threading of macrocycles onto the polymer chains is a noncovalent modification of the macromolecules that affects the properties, such as solubility and reactivity as well as the mechanical, electrical, and processing properties. ,− The solubility of a polymer can be enhanced by polyrotaxane formation due to the shielding effect exerted by the threaded rings, preventing molecular interactions between the polymer chains, such as hydrophobic or π–π interactions. − Polyrotaxanes can also be cross-linked through reactive functionalities on the macrocycles, resulting in so-called slide ring gels that may exhibit self-healing properties, high degrees of swelling, and elongations at break due to the movable cross-links. − Among crown ethers, − cucurbiturils, − calixarenes, and cyclodextrins (CDs), , CDs are the most commonly used class of cyclic molecules in polyrotaxane synthesis because CDs are nontoxic, biodegradable, available on the industrial scale, and easily functionalizable. , However, the large-scale synthesis of polyrotaxanes remains challenging despite the many polyrotaxanes that have been previously reported in the literature. The so-called threading approach, which is most commonly used for polyrotaxane synthesis, involves threading the macrocycle onto a given polymer followed by attachment of stopper groups.…”