Noncovalently assembled hydrogels

Another exciting development for hydrogels is self-assembly. Self-assembly means that the constituent molecules of a material organize themselves, under thermodynamic equilibrium, into a well-defined and stable configuration, held together by noncovalent bonds. The structural form of the molecules determines the way they fit together, and this can be influenced by environmental factors including temperature and pH value. ... 

This article provides an overview of the recent progress in fundamental studies, preparation, characterization, and application of nanofibrillar hydrogels formed by physical (noncovalent) cross-linking of one-dimensional (ID) supramolecular building blocks of synthetic and biological polymers. High-aspect-ratio nanofibrils, as focused on in the present review, are formed by autonomous association (self-assembly) of individual molecules and not by their forced fabrication (directed... 

Figure 3 Environmentally triggered folding, self-assembly, and noncovalent fibril cross-linking leading to hydrogel formation. Crosslinks are formed by the irregular facial self-assembly of hairpins. (Reproduced from Ref. 67. Springer, 2006.)...

There are two main classes of hydrogels (Figure 2.1), those composed of three-dimensional networks of cross-linked polymer chain strucmres that are insoluble in water chemical hydrogels) and those produced by the self-assembly of (macro) molecules to form noncovalent structures physical hydrogels). 

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