Supramolecular design in biopolymers and biomimetic polymers for properties

This mini review uses two examples to illustrate the importance of supramolecular chemistry in natural and biomimetic polymers for advanced mechanical properties. In the first example, dragline silk, one of the strongest and toughest natural fibers, uses intermolecular weak forces to self-assemble into nanocomposites composed of beta-sheet nanocrystals imbedded in an amorphous matrix. In the second example, a load-bearing protein, the sarcomere muscle protein titin, uses intramolecular weak forces to fold into repetitive modules for combined strength, toughness, and elasticity. Both examples show vividly that many natural polymers can combine important mechanical properties through programming supramolecular weak interactions into covalently formed biopolymers. This mini review attempts to summarize the current understanding of the molecular mechanisms that contribute to the exceptional mechanical properties for each natural polymer. Following that, the efforts from others and the author's own laboratory on developing synthetic polymers to mimic these natural counterparts are discussed. (C) 2007 Society of Chemical Industry.