Polymers, reversible supramolecular

Finally, Chap. 6 deals with the exploitation of biocatalysis in generating supramolecular polymers, a class of polymers where the monomers are connected via non-covalent bonds. This approach provides highly dynamic and reversible supramolecular structures, inspired by biological polymeric systems found in the intra- and extracellular space. A number of potential applications of enzymatic supramoleular polymerizations are discussed in the context of biomedicine and nanotechnology. 

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. 

Sonpens SHM, Sijbesma RP, van Genderen MHP, Meijer EW. Selective formation of cyclic dimers in solutions of reversible supramolecular polymers. Macromolecules. 2001 34 3815-3818. 

Knoben W, Besseling NAM, Bouteiller L, Stuart AC (2005) Dynamics of reversible supramolecular polymers independent determination of the dependence of linear viscoelasticity on concentration and chain length by using chain stoppers. Phys Chem Chem Phys 7 (ll) 2390-2398... 

Knoben W, Besseling NAM, Stuart MAC (2006) Chain stoppers in reversible supramolecular polymer solutions studied by static and dynamic light scattering and osmometry. Macromolecules 39(7) 2643-2653... 

Block co-polymer which use reversible supramolecular interactions like hydrogen bonding can form materials with interesting properties. As the interactions are reversible, more control can be exercised and the properties can be minutely controlled. Meijer and coworkers have designed an ureidotriazine (UTr) based systems, which on combination with poly (ethylene/butylenes) give rise to rod-coil systems [14]. 

Bifunctional UPy derivatives with low molecular weight have been instrumental in demonstrating the feasibility of linear, reversible supramolecular polymers with high degrees of polymerization. 

Reversible supramolecular interactions in polymers can be achieved via several mechanisms, such as hydrogen bonding, exemplified by the ure-idopyrimidinone unit (Bosman et al, 2004 Montarnal et al, 2009), metal coordination chemistry (Fiore et al, 2011 Kumpfer et al, 2010), or k-k stacking, such as that seen with triphenylene units (Buratini et al, 2009). These materials can heal autonomously in a few cases, but in most cases also need stimuli for their healing action such as temperature or pressure. 

Knoben, W., Besseling, N.A.M., and Cohen Stuart, M.A. (2(X)7) Rheology of a reversible supramolecular polymer studied by comparison of the effects of tenq>erature and chain stoppers. Journal of Chemical Physics, 126,024907/ 024901-024907/024909. 

Hydrogen bonding interactions are important for the development of selfassembling supramolecular materials, which are defined as materials in which monomeric units are reversibly bound via secondary interactions to form polymer-like stmctures that exhibit polymeric properties in solution as well as in bulk (Bmnsveld et al. 2001). Rotello used hydrogen bond functional polymers to direct the formation of large vesicles (lUian et al. 2000), reversibly attach polymers on... 

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