Catenanes, entanglement

Until recendy assemblies consisting of two or more independent infinite ID, 2D, or 3D structures that interpenetrate were rare, but examples are now being reported with ever-increasing frequency. Catenane and/or rotaxane associations, infinitely repeated in an orderly manner, are an intrinsic feature of these entanglements. 

White, J.H., Millett, K.C., Cozzarelli, N.R. (1987) Description of the topological entanglement of DNA catenanes and knots by a powerful method involving strand passage and recombination. J. Mol. Biol. 197, 585-603. 

Dietrich-Buchecker, C., Leize, E., Nierengarten, J. F., Sauvage, J. P, Vandorsselaer, A., Singly and doubly interlocked [2]-catenanes - influence of the degree of entanglement on chemical-stability as estimated by fast-atom-bombardment (Fab) and electrospray-ionization (Esi) mass spectrometries (Ms). J. Chem. Soc., Chem. Commun. 1994, 2257-2258. 

Unlike the cyclic catenanes, rotaxanes are simpler species originally proposed by Wasserman and first demonstrated by Harrison [77], In these systems a cyclic molecule is threaded on a rigid or flexible molecular axle, attracted by complementary binding sites, to form a pseudorotaxane. Under normal entropically driven supramolecular chemistry the cyclic component would eventually slip off one or other end of the central axle, however, it can be kept in place if both ends of the axle react with bulky groups while the macrocycle is still threaded. Alternatively a macrocycle can be formed around an axle molecule that already possesses bulky termini, as shown in Fig. 1.22. Either method leads to an entanglement in which the cycle species can move along the thread without ever coming off. 

Interpenetrating polymer networks (IPNs) are relatively novel types of polymer alloys consisting of two or more crosslinked polymers held together by permanent entanglements with only accidental covalent bonds between the polymers, i.e. they are polymeric catenanes (1-6). 

Entangled systems are extended arrays, more complex than their constituents, that are comprised of individual motifs forming, via interlocking or interweaving, periodic architectures infinite in at least one dimension. Simple interdigitation is not considered here. As previously stated, most of the entangled arrays can be considered regularly repeated infinite versions of finite molecular motifs like catenanes, rotaxanes and pseudo-rotaxanes. 

There are few examples of ID networks interpenetrating, perhaps due to the requirement of ring motifs of suitable size to be present so that the catenane-like interactions needed can be formed. Nonetheless, ID networks can interpenetrate in different ways, leading to entanglements... 

Interpenetrating networks have an obvious relationship to molecular catenanes indeed, they can be thought of simply as catenated polymers. Similarly, entangled networks with rotaxane-like relationships have also been reported. ... 

When the polymerization of DT was performed in the presence of tydic poly(oxyethylene) (CPO), the product included a catenane stracture of cyclic poly(DT) and CPO entangled with each other. It was concluded that the poly(DT) obtained from polymerization of DT includes a polycatenane structure. ... 

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