Conductive regenerated silk fibroin composite fiber containing MWNTs

Abstract

The electrically conductive regenerated silk fibroin (RSF) fiber containing multiwalled carbon nanotubes (MWNTs) was developed through wet spinning process. A general scheme used for extraction of RSF powder as biopolymer matrix for MWNTs conductive filler. The MWNTs inclusion demands for a sophisticated approach to prepare stable, exfoliated and well distributed filler in matrix solution. Dynamic Light Scattering (DLS) was utilized to show the ability of RSF in stabilizing of MWNTs throughout spinning solution. A non-Newtonian shear thinning behavior observed for RSF/MWNTs according to strong chain entanglement, whereas, the neat RSF solution shows a lower dependence on the shear rate. The scanning electron microscopy (SEM) images also confirmed the proper distribution of MWNTs as a continuous fibril media in the RSF matrix. The Fourier transform infrared spectroscopy (FTIR) demonstrated the role of MWNTs inclusion for increasing of the crystalinity compared to bare RSF fiber. The Raman spectra also confirmed the domination of RSF signatures by strong Raman bands of MWNTs most specifically in RBM region regarding to superior nanotube exfoliation. Moreover, the measurement of four-point probe electrical conductivity for different MWNTs content shows a maximum conductivity of 0.12 S/cm at percolation threshold. The higher thermal stability and greater crystalinity were also evidenced by DSC thermal analysis.