Fabrication and properties of conductive conjugated polymers/silk fibroin composite fibers

Highly conductive polymers (polypyrrole, polyaniline or poly3,4-ethylene-dioxythiophene)/silk fibroin composite fibers were fabricated successfully and expediently by in situ polymerization without any modification of silk fibroin surface. Scanning electron microscopy (SEM) and optical microscope confirmed the silk fibroin fiber surface covered entirely by conductive polymers. Polypyrrole/silk fibroin (PPY/SF), polyaniline/silk fibroin (PANI/SF), and poly3,4-ethylene-dioxythiophene/silk fibroin (PEDOT/SF) composite fibers exhibited varied conductivity in the range of 3.8–4.2 × 10−1, 0.9–1.2 × 10−2 and 4.9–5.2 × 10−3 S cm−1, respectively. Improved thermal stability of silk fibroin fiber via coating process was observed from thermogravimetric analysis (TGA) results. Structural analysis indicated that the interactions including hydrogen-bonding and electrostatic attraction existed between silk fibroin macromolecules and conductive polymers. The peptide linkages bearing on silk fibroin macromolecules played an important role in the in situ polymerization by attracting conjugated cation radicals. These composite fibers still possessed former fibrillar morphology and strength properties.