Hydrogen bond polymer architectures

The structures described include those previously discussed elsewhere (miktoarm stars, combs, grafts, rings, dendritic, hyperbranched and arborescent), as well as newly synthesized complex architectures (multicyclic, hydrogen-bonded complex architectures, structures from living alkene polymerization, ADMET and polyhomologation, as well as topological polymer chemistry). 

Supramolecular architectures in which transition metal cationic centres are linked via hydrogen-bonded supramolecular synthons [1,2] comprise an increasingly important class of inorganic co-ordination polymers [3], owing to their multi-dimensional, multi-functional network structures. 

The design and synthesis of supramolecular architectures with parallel control over shape and dimensions is a challenging task in current organic chemistry [13, 14], The information stored at a molecular level plays a key role in the process of self-assembly. Recent examples of nanoscopic supramolecular complexes from outside the dendrimer held include hydrogen-bonded rosettes [15,16], polymers [17], sandwiches [18, 19] and other complexes [20-22], helicates [23], grids [24], mushrooms [25], capsules [26] and spheres [27]. 

Edgecombe BD, Stein JA, Frechet JMJ, Xu Z, Kramer EJ. The role of polymer architecture in strengthening polymer— polymer interfaces a comparison of graft, block, and random copolymers containing hydrogen-bonding moieties. Macromolecules 1998 31 1292-1304. 

A relatively new field called supramolecular chemistry has been developed over the last three decades. Supramolecular assemblies and supramolecular polymers differ from macromolecules, where the monomeric units are covalently linked. In a supramolecular polymer, the monomeric units self-assemble via reversible, highly directional, noncova-lent interactions. These types of bonding forces are sometimes called secondary interactions. Hydrogen bonding is the secondary force most utilized in supramolecular chemistry, but metal coordination and aromatic tt-tt electronic interactions have also been used. From a materials standpoint, supramolecular assemblies are promising because of the reversibility stemming from the secondary interactions. The goal is to build materials whose architectural and dynamical properties can respond reversibly to external stimuli. Solid phases are prepared by self-assembly from solution. In the solid-state, supramolecular polymers can be either crystalline or amorphous. 

Fig.1 Architectures of different hydrogen bonded, supramolecular polymers (A hydrogen-bonding acceptor D = hydrogen-bonding donor)...

Similar to supramolecular polymers bearing hydrogen bonds within their main chain, side-chain architectures are possible in a similar manner. Usually,... 

In addition to this classical polarity effect, the solvent can have a more subtle influence, hi the case of monomer 16 (Fig. 20) hydrogen bonding in chloroform leads to the formation of a usual flexible supramolecular polymer. However, in dodecane the dimerization of the ureidotriazine is reinforced by a solvophobic stacking of the aromatic parts, which yields a columnar architecture [93]. A similar solvophobic effect has been demonstrated with a UPy-based monomer [94]. Another possible side effect of the nature of the solvent is the occurrence of specific host-guest interactions between the HBSP and the solvent [42,95,96]. 

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