Preparation of conductive silk fibroin yarns coated with polyaniline using an improved method based on in situ polymerization

Abstract

In situ polymerization is a prominent current topic in the research of skin-core structure polyaniline (PANI) conductive fibers owing to its advantages such as the convenience of preparation and high conductivity of fiber, but it is difficult to realize the continuous fabrication of conductive fibers using this method. In our previous work, we presented a novel method based on in situ polymerization and achieved the continuous fabrication of conductive yarns. In order to reduce the consumption of raw materials such as aniline, doping acid, and oxidant in the preparation, a further improvement is proposed in this paper. Electrical conductive silk fibroin (SF) yarns covered with PANI were prepared by using an improved method based on in situ polymerization. The results show that the improved method has lower consumption than the previous method, and the reduction of raw materials can reach more than 90% compared to the previous method. The structure and properties of the treated SF yarns were studied in detail. The treated SF yarns characterized using scanning electron microscopy and Fourier transform infrared spectroscopy improved the surface of the SF fibers and the gaps between them were covered by conductive PANI; further, interactions such as van der Waals' force, electrostatic interaction, and hydrogen bonding existed between the SF macromolecules and PANI. Thermogravimetric analysis indicated that the thermal stability of the treated yarns was reduced owing to the existence of PANI. The treated yarns exhibited good conductive properties; with the increase in oxidant concentration, the conductivity of coated yarns increased first and thereafter decreased; the maximum conductivity of coated yarn could reach 60S/m, and the maximum conductivity of PANI was as high as 180S/m. Compared to the SF yarn, the breaking strength, breaking elongation, and initial modulus of coated yarns were reduced and the loss was increased with the increase in oxidant concentration.