Ultra strong pyroprotein fibres with long-range ordering

Abstract

Silks are protein-based natural structured materials with an unusual combination of high strength and elongation. Their unique microstructural features composed of hard beta-sheet crystals aligned within a soft amorphous region lead to the robust properties of silks. Herein we report a large enhancement in the intrinsic properties of silk through the transformation of the basic building blocks into a poly-hexagonal carbon structure by a simple heat treatment with axial stretching. The carbon clusters originating from the beta-sheet retain the preferred orientation along the fibre axis, resulting in a long-range-ordered graphitic structure by increasing heat-treatment temperatures and leading improvements in mechanical properties with a maximum strength and modulus up to similar to 2.6 and similar to 470 GPa, respectively, almost four and thirty times surpassing those of raw silk. Moreover, the formation of sp(2) carbon configurations induce a significant change in the electrical properties (e.g. an electrical conductivity up to 4.37 x 10(3) S cm(-1)).