Regensburg 2010 – scientific programme

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SYMR: Symposium Nuclear Magnetic Resonance: from Applications in Condensed-Matter Physics to New Frontiers

SYMR 7: Biopolymers and Biomaterials

SYMR 7.2: Talk

Wednesday, March 24, 2010, 14:30–14:45, H37

Interplay between nanostructure and mechanical properties in natural and artificial polymer fibers — •Periklis Papadopoulos, Roxana Ene, and Friedrich Kremer — Universität Leipzig, Institut für Experimentelle Physik I

The comparison of mechanical with infrared spectroscopy can be used to explore the multi-level nanostructure of semi-crystalline polymers. In this study we attempt to determine the interconnection of the nanocrystal and amorphous phases in two states of spider dragline silk, native and supercontracted with water, and compare it with artificial systems, such as polyamide 6. Crystal stress can be measured with a high time resolution through the analysis of frequency shifts of absorption bands, while varying mechanical fields are applied. The results show that in both states of silk a serial arrangement between the crystalline and amorphous phase dominates the nanostructure. Polyamide 6 films and electrospun fibers have a similar morphology. In silk, however, water can break the hydrogen bonds of the amorphous chains, and, in combination with hydrophobic effects, it induces the formation of a physical network in the amorphous phase. This network increases in stiffness, until a stress limit is reached. At higher stress, the nanostructure of supercontracted silk is irreversibly transformed to one similar to native silk. This enables one to make a complete description of the mechanical properties of silk in both states, by taking into account the energy required to break these bonds in the previous structural model that assumed a pre-strain distribution of worm-like amorphous chains.