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Nat Mater. 2005 Dec;4(12):901-5. Epub 2005 Nov 20.

Relationships between supercontraction and mechanical properties of spider silk.

Author information

1
Department of Macromolecular Science and The Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Fudan University, Shanghai 200433, PR China.

Abstract

Typical spider dragline silk tends to outperform other natural fibres and most man-made filaments. However, even small changes in spinning conditions can have large effects on the mechanical properties of a silk fibre as well as on its water uptake. Absorbed water leads to significant shrinkage in an unrestrained dragline fibre and reversibly converts the material into a rubber. This process is known as supercontraction and may be a functional adaptation for the silk's role in the spider's web. Supercontraction is thought to be controlled by specific motifs in the silk proteins and to be induced by the entropy-driven recoiling of molecular chains. In analogy, in man-made fibres thermal shrinkage induces changes in mechanical properties attributable to the entropy-driven disorientation of 'unfrozen' molecular chains (as in polyethylene terephthalate) or the 'broken' intermolecular hydrogen bonds (as in nylons). Here we show for Nephila major-ampullate silk how in a biological fibre the spinning conditions affect the interplay between shrinkage and mechanical characteristics. This interaction reveals design principles linking the exceptional properties of silk to its molecular orientation.

PMID:
16299506
DOI:
10.1038/nmat1534
[Indexed for MEDLINE]

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