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1. Synthesis of linear [7]- and [8]catenanes

   https://doi.org/10.1016/j.xcrp.2023.101767  

   Harlan, Gray H; Tran, Sheila L; Colley, Nathan D; Nosiglia, Mark A; Zhang, Yipei; Barnes, Jonathan C (January 2024, Cell Reports Physical Science)

   Catenanes are a family of mechanically interlocked molecules that consist of molecular rings that can be interlocked to give linear, radial, or cyclic structures. Although chemists have pursued extended linear poly[n]catenane architectures for many decades, there still exists a fundamental gap between the synthesis of well-defined, linear oligomers and that of disperse polymers that are often produced as a mixture of architectures. Here, we report two convergent one-pot syntheses that “zip-tie” together two pre-made [3]catenanes by first using orthogonal metal templation with phenanthroline (Cu(I)) and terpyridine (Fe(II)) ligands. These pre-catenate complexes were subjected to a ring-closing metathesis step to afford discrete, linear [7]- and [8]catenanes. The successful synthesis and isolation of the discrete [7]- and [8]catenanes were confirmed using multiple methods of characterization. Because these record-setting linear [n]catenanes possess open phenanthroline metal-binding sites at each end, further expansion to all-interlocked linear poly[n]catenanes is a realistic proposition. 

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2. Material properties and applications of mechanically interlocked polymers

   https://doi.org/10.1038/s41578-021-00278-z  

   Hart, Laura F.; Hertzog, Jerald E.; Rauscher, Phillip M.; Rawe, Benjamin W.; Tranquilli, Marissa M.; Rowan, Stuart J. (January 2021, Nature Reviews Materials)

   null (Ed.)

   Mechanically interlocked polymers (MIPs), polymer architectures that incorporate the mechanical bond, have seen a dramatic growth in interest over the last decade or so. Of particular interest in these architectures are the high mobility and conformational freedom of the interlocked components, which can give rise to unique property profiles. Over the years the research advances, from the chemistry, physics, material science and engineering fields, has started to build an understanding of how incorporating mechanical bonds into a polymer structure impacts its properties. This review focuses on summarizing the state-of-the-art understanding of the structure-property relationships in these materials and an outlook toward their applications, specifically focusing on four main classes of MIPs, polyrotaxanes, slide-ring gels, daisy-chain polymers and polycatenanes. 

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3. Exploring the Impact of Ring Mobility on the Macroscopic Properties of Doubly Threaded Slide‐Ring Gel Networks

   https://doi.org/10.1002/anie.202411172  

   Oh, Jongwon; Liu, Guancen; Kim, Hojin; Hertzog, Jerald E; Nitta, Natsumi; Rowan, Stuart J (September 2024, Angewandte Chemie International Edition)

   Abstract The integration of mechanically interlocked molecules (MIMs) into polymeric materials has led to the development of mechanically interlocked polymers (MIPs). One class of MIPs that have gained attention in recent years are slide‐ring gels (SRGs), which are generally accessed by crosslinking rings on a main‐chain polyrotaxane. The mobility of the interlocked crosslinking moieties along the polymer backbone imparts enhanced properties onto these networks. An alternative synthetic approach to SRGs is to use a doubly threaded ring as the crosslinking moiety, yielding doubly threaded slide‐ring gel networks (dt‐SRGs). In this study, a photo‐curable ligand‐containing thread was used to assemble a series of metal‐templated pseudo[3]rotaxane crosslinkers that allow access to polymer networks that contain doubly threaded interlocked rings. The physicochemical and mechanical properties of these dt‐SRGs with varying size of the ring crosslinking moieties were investigated and compared to an entangled gel (EG) prepared by polymerizing the metal complex of the photo‐curable ligand‐containing thread, and a corresponding covalent gel (CG). Relative to the EG and CG, the dt‐SRGs exhibit enhanced swelling behavior, viscoelastic properties, and stress relaxation characteristics. In addition, the macroscopic properties of dt‐SRGs could be altered by “locking” ring mobility in the structure through remetalation, highlighting the impact of the mobility of the crosslinks. 

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4. Effect of metallosupramolecular polymer concentration on the synthesis of poly[ n ]catenanes

   https://doi.org/10.1039/D1SC02450G  

   Tranquilli, Marissa M.; Wu, Qiong; Rowan, Stuart J. (January 2021, Chemical Science)

   null (Ed.)

   Poly[ n ]catenanes are a class of polymers that are composed entirely of interlocked rings. One synthetic route to these polymers involves the formation of a metallosupramolecular polymer (MSP) that consists of alternating units of macrocyclic and linear thread components. Ring closure of the thread components has been shown to yield a mixture of cyclic, linear, and branched poly[ n ]catenanes. Reported herein are investigations into this synthetic methodology, with a focus on a more detailed understanding of the crude product distribution and how the concentration of the MSP during the ring closing reaction impacts the resulting poly[ n ]catenanes. In addition to a better understanding of the molecular products obtained in these reactions, the results show that the concentration of the reaction can be used to tune the size and type of poly[ n ]catenanes accessed. At low concentrations the interlocked product distribution is limited to primarily oligomeric and small cyclic catenanes . However, the same reaction at increased concentration can yield branched poly[ n ]catenanes with an ca. 21 kg mol −1 , with evidence of structures containing as many as 640 interlocked rings (1000 kg mol −1 ). 

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5. The effect of thread-like monomer structure on the synthesis of poly[ n ]catenanes from metallosupramolecular polymers

   https://doi.org/10.1039/d2sc05542b  

   Tranquilli, Marissa M.; Rawe, Benjamin W.; Liu, Guancen; Rowan, Stuart J. (March 2023, Chemical Science)

   The main-chain poly[ n ]catenane consists of a series of interlocked rings that resemble a macroscopic chain-link structure. Recently, the synthesis of such intriguing polymers was reported via a metallosupramolecular polymer (MSP) template that consists of alternating units of macrocyclic and linear thread-like monomers. Ring closure of the thread components has been shown to yield a mixture of cyclic, linear, and branched poly[ n ]catenanes. Reported herein are studies aimed at accessing new poly[ n ]catenanes via this approach and exploring the effect the thread-like monomer structure has on the poly[ n ]catenane synthesis. Specifically, the effect of the size of the aromatic linker and alkenyl chains of the thread-like monomer is investigated. Three new poly[ n ]catenanes (with different ring sizes) were prepared using the MSP approach and the results show that tailoring the structure of the thread-like monomer can allow the selective synthesis of branched poly[ n ]catenanes. 

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