Polyrotaxanes topology

Oku, T. Furusho, Y Takata, T. A concept for recyclable cross-linked polymer Topologically networked polyrotaxane capable of undergoing reversible assembly and disassembly. Angew. Chem. Int. Ed. 2004, 43, 966-969. 

Okumura Y, Ito K. The polyrotaxane gel a topological gel by figure-of-eight cross-links. Adv Mater 2001 13 485-487. 

A totally new situation arises from the presence of defined topological bonds in polymer systems. The last documented example is given by polyrotaxanes 7 in which defined topological bonds occur between the macrocycles and the polymer chain (considered as infinite). The polyrotaxanes are composed of a polymer chain on to which a certain number of macrocycles is threaded. For short polymer chains, the end-capping by stoppers prevents the macrocycles unthreading from the chain [27, 28] (Scheme 3). Multicatenanes 8 are structurally related to polyrotaxanes 7 and can be viewed as cyclic analogs of polyrotaxanes [29]. 

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... 

All the polyrotaxanes discussed thus far are based on linear backbones. Viewing new properties and applications of branched and cross-linked polymers, three-dimensional polyrotaxanes will surely be interesting in terms of both topology and potential applications. Gong and Gibson extended the hydrogen-bonding theo-... 

As their structures define, polyrotaxanes are polymeric composites. Their ultimate properties are related both to the chemical compositions of the cyclic and backbone and to their relative proportions. However, because of its different topology relative to simple mixtures, the interpenetrated structure introduces new outcomes in terms of properties. Because the applications of materials rely on their properties, these aspects are incorporated into this section. 

As noted in the above sections, polyrotaxanes, noncovalent supramacromolecules, have drawn great interest from scientists world-wide. They are novel in terms of both topology and ultimate properties compared with chemically bonded polymers. 

Because of their novel topologies, polyrotaxanes have properties different from those of conventional polymers. Solubility, intrinsic viscosity, melt viscosity, glass transition, melting temperature and phase behavior can be altered by the formation of polyrotaxanes. The detailed changes are related both to the properties of the threaded cyclics and to the backbone and the threading efficiency. 

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. 

This chapter describes the structures and properties of supramolecular silver complexes with specific topologies such as cages, tubes, catenanes and polycate-nanes, rotaxanes and polyrotaxanes, and multidimensional frameworks, as synthesized by reactions of various silver salts with predesigned organic ligands. 

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... 

The binuclear terbium centers and type I rotaxanes form a two-dimensional layer. Stacked layers are further interconnected via type II rotaxanes to form a three-dimensional polyrotaxane network, which has an inclined a-polonium topology with the binuclear terbium centers behaving as six-connected nodes (Fig. 20.4.10). The void space in the crystal packing is filled by a free rotaxane unit, NOJ and OH- counter ions, and water molecules. 

Not only poly-pseudo-rotaxanes but also polyrotaxanes should be considered trivial topological entanglements, extending the concepts developed for the related molecular entities. By means of ideal continuous deformations we could separate the components of any finite portion of a polyrotaxane. How-... 

One of the focuses in CyD applications is their use as components of devices in systems with nontrivial topological properties, i.e. catenanes, rotaxanes [1-8], and polyrotaxanes [1, 9,10] presented in some detail in Chapter 12. For a recent review of interlocked assemblies see Ref [11]. This is a part of novel "bottom up approach to the construction of devices on the basis of one molecule or one molecular aggregate [12]. 

E and F). The essential difference in the main-chain structure between the two types of polyrotaxanes causes large differences in their physical or mechanical properties. Polyrotaxanes A-D are further divided into main- (A and B) and side-chain type (C and D). Meanwhile, the synthesis of poly[2]rotaxane (E) and poly[3]rotaxane (F) has been very recently achieved. Genuine poiyrotaxane seems to be one of the polyrotaxanes like the latter topological polyrotaxanes, which may reflect their truly unique structures to their properties. 

Topologically linked poly[2]rotaxane is called daisy-chain-type polyrotaxane. Since Stoddart and coworkers attempted to construct a supramolecular poly[2]rotaxane (poly-pseudo[2]rotaxane) in 1998, many researchers have tried to prepare the daisy-chain-type polyrotaxane. However,... 

Scheme 16 Gibson s topological polyrotaxane network synthesis.

Scheme 17 Ito s topological pol)Totaxane gels prepared by the cross-linking of main-chain-type polyrotaxane.

Yui et al. also developed biodegradable hydrogels cross-linked by topological bonds. Polyrotaxanes consisting of... 

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