Synthesis and characterization of polypyrrole-graft-poly(ε-caprolactone) copolymers: new electrically conductive nanocomposites

A series of polypyrrole-graft-poly(ε-caprolactone) (PPy-g-PCL) copolymers have been synthesized via oxidative copolymerization of pyrrole and pyrrole-end functional macromonomers. Copolymerizations were carried out in tetrahydrofuran at 0 °C using FeCl3 as the oxidizing and doping agent. Poly(ε-caprolactone) rich copolymers (>85 wt.%) were partly soluble in common organic solvents, whereas polypyrrole-rich copolymers were completely insoluble. The composition of the PPy-g-PCL copolymers was determined by Fourier transform infra-red (FTIR) spectroscopy and thermal gravimetrical analysis (TGA). By controlling the monomer feed and molecular weight of the macromonomer, graft copolymers across a broad composition range were obtained. Both differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) show that the PPy-g-PCL copolymers phase separate into PPy and PCL rich domains. The electrical conductivity of the nanocomposites increases with the amount of polypyrrole in the copolymer between the value of pure PCL (10−12 S/cm) and that of polypyrrole (10 S/cm). Atomic force microscopy (AFM) confirmed the presence of nanophases (15–40 nm) and hence, the preparation of new nanomaterials.