Noncovalent Chemistry-Supramolecular Polymers

Other noncovalent interactions, such as the hydrophobic effect, ionic interactions, or n-n interactions, are even weaker than hydrogen bonding, and suffer 

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It was recently suggested that carbamate bonds could be employed for a wider variety of dynamic covalent chemistry (DCC) experiments (88) and DCC is quickly emerging as a promising alternative to noncovalent self-assembly (91). This experiment offers an elegant opportunity of performing supramolecular chemistry with covalent bonds. One of the most important advantages here is the robustness of covalently organized structures, which on the other hand can be reversibly broken, at will. Of particular interest are supramolecular polymers and supramolecular materials. 

By connecting polymeric blocks via a noncovalent interaction, it is possible to obtain supramolecular diblock [80], triblock [81], or multiblock copolymers [82] (Figure 34.18). Supramolecular graft polymers are also possible [83] in fact, a very early event of supramolecular polymer chemistry that actually predated the studies of Lehn was the development of side chain-functionahzed polymers by Kato and Frechet [84]. In most cases, hydrogen-bonding arrays are used, due to their strength and directionality. 

Since this book provides a wide selection of relevant topics presented by some of the major actors in the domain, we shall emphasize here the conceptual and prospective aspects, illustrated by a brief retrospective of our own work. It started with the exploration of the concept of supramolecular polymers, introduced in 1990 [3a], through the implementation of the principles of supramolecular chemistry to generate polymers and liquid crystals of supramolecular nature from molecular components interacting through specific hydrogen-bonding patterns. The chemistry of supramolecular polymeric entities based on these as well as on other types of noncovalent interactions has since then actively developed [3-17]. 

RgurelS An aspect of the panorama of supramolecular polymer chemistry formation of different types of polymeric supermolecular entities by recognition-directed self-assembly of monomers through noncovalent interactions, such as hydrogen bonds. 

Supramolecular chemistry thus has a direct relationship with the highly active area of combinatorial chemistry, however in a very specific fashion. Indeed, reversibility being a basic and crucial feature of supramolecular systems, the dynamic generation of supramolecular diversity from the reversible combination of noncovalently linked building blocks falls within the realm of the emerging area of dynamic combinatorial chemistry (DCC) which involves dynamic combinatorial libraries, of either virtual (VCL) or real nature depending on the system and the conditions [45,46], The concepts and perspectives of the DCCA CL approach have been outlined, inter alia with respect to supramolecular polymers [45],... 

As a scientific concept, supramolecular polymers have received increasing attention in recent years. The introduction of concepts from supramolecular chemistry in polymer science have led to the development of polymers in which the main chain is held together by noncovalent interactions such as hydrogen bonds, 7r-stacking, and coordination interactions. In the present chapter, we will discuss how the scientific developments in a specific class of supramolecular polymers — quadruple hydrogen-bonded supramolecular polymers — is now rapidly leading to applications that take advantage of the unique mechanical properties of these materials. 

This section discusses the scope of [60]fullerene-based polymer chemistry. These approaches may allow for the development, on a supramolecular level, of unprecedented architectures. Previous sections have dealt primarily with the self-assembly of the [60]fullerene and its derivatives as a result of microphase separation and subsequent formahon of huge [60]fullerene clusters driven by the weak noncovalent forces in the solid state, mesophase and water. To avoid microphase separation, the introduction of functionalized [60]fullerene derivatives into polymer main chains through noncovalent interactions is a very promising approach. The construction of fullerene-containing supramolecular polymers in organic solution is now presented. 

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