Polycatenanes and Polyrotaxanes

8 Raymo, F. M. and Stoddart, J. F., Polymers with intertwined superstructures and interlocked structures , in Supramolecular Polymers, Ciferri, A. (Ed.), Dekker New York, 2000. 

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Supramolecular chemistry allows novel kinds of polymer linkages such as the mechanical links found in polycatenanes and polyrotaxanes. 

The ring topology is the potential to form unique polymer structures. Like linear polymers, cyclic polymers not only can be branched or cross-linked, but also can form non-covalently linked structures based on their loop topology. These are referred to as topological polymers, including rotaxane, catenane, threaded rings, and rings threaded by network chains. Recently, much attention has been paid to how their particular properties not only differ from linear polymers, but also how they differ from a component of an interlocked polymer system, such as polycatenanes and polyrotaxanes. 

In addition to the infinite tubes, polycatenanes, and polyrotaxanes, all of which are polymeric complexes, a great number of silver coordination polymers with ID, 2D and 3D framework structures have been reported more recently. Selected examples and their specific topologies of some of these are listed in Table 11.1. Schematic structures of the corresponding organic ligands are shown in Figure 11.23.9,58-75... 

It is diflicult to forecast the ways for a practkal applkation of the imw types of polymeric compounds — polycatenanes and polyrotaxanes — which to a certain extent is due to the diflkulties of their synthesis. It can be, however, expected that a detailed study of their jdiysical and mechanical proj rties, which will oj n the ways for their practical application, will become possible as the synthetic techniques ate developed and simpler ways for the synthesis are found. 

Macromolecules incorporating repeating units connected by covalent bonds are widespread in nature [1], Synthetic procedures for the construction of their artificial counterparts are well established [2], Furthermore, the properties of these unnatural macromolecules are now rather well understood and, indeed, polymeric materials have found applications in numerous branches of science and technology [2], In recent years, synthetic chemists have learned how to introduce mechanical bonds (Fig. 1) into small molecules. Mechanically interlocked rings, as well as wheels mechanically trapped onto axles, can be constructed efficiently to afford molecular compounds, named catenanes and rotaxanes, respectively.t Metal coordination [18-32], donor/acceptor interactions [33-43], hydrogen bonds [44-64] and/or hydrophobic interactions [65-78] between appropriate components have all been employed to template the formation of these exotic molecules. Making the transition from simple catenanes and rotaxanes to their macromolecular counterparts—namely, polycatenanes and polyrotaxanes. 

Takata, T., Kihara, N. and Furusho, Y. Polyrotaxanes and Polycatenanes Recent Advances in Syntheses and Applications of Polymers Comprising of Interlocked Structures. Vol. 171, pp. 1-75. 

The interest in macromolecular systems containing defined topological bonds, such as polyrotaxanes 7, multicatenanes 8, polycatenanes 9, poly[2]catenanes 10, and polymeric catenanes 11, is dual. First, these macromolecules represent daunting synthetic and characterization challenges which deserve attention in their own... 

Besides simple rotaxanes and catenanes, a great variety of more complex systems have been synthesized, including branched [n]rotaxanes [26a], [n]rotaxanes bearing dendritic stoppers [26b], catenanes composed by two, three, five, or seven interlocked macrocycles [26c,e], polyrotaxanes and polycatenanes [2-6, 8], catenanes with very special shapes [27], rotocatenanes [28], pretzelanes [29], and knots [4], Some of these compounds are shown in Figure 8. 

Polyrotaxanes and Polycatenanes Recent Advances in Syntheses and Applications... 

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