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 ?-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 ?-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 ?2.6 and ?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?×?10³?S?cm^-1).The mechanical properties of silk are determined by tight stacks of sheet-like peptide crystals distributed in amorphous regions. Here, the authors heat and stretch silk fibres to align these crystal into a long range ordered carbon structure and dramatically enhance the silk strength.

SUBMITTER: Cho SY 

PROVIDER: S-EPMC5509745 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature