Physical properties of poly(vinylidene fluoride) composites with polymer functionalized multiwalled carbon nanotubes using nitrene chemistry

Abstract

Poly(methyl methacrylate) (PMMA) functionalized multi-walled carbon nanotubes (MWNT) (f-MWNT) are prepared using nitrene chemistry and atom transfer radical polymerization. The >C=O groups in the f-MWNT interact with the >CF₂ groups of poly(vinylidene fluoride) (PVDF) to achieve a compatible blend. An increase of the glass transition temperature (T_g), relaxation temperatures of the crystal-amorphous interface and crystalline phases are observed in the composites over pristine PVDF. The thermal stability of the composites increases with increasing f-MWNT concentration. The storage modulus increases significantly with increasing f-MWNT concentration and the highest increase of 120% over PVDF is observed for 1 wt% f-MWNT at 50 °C. An increase in tensile strength with a decrease of the strain at break, and increase of Young's modulus and toughness indicate the formation of a very hard and ductile composite material. The electrical conductivity is high (1 × 10⁻⁴ S cm⁻¹, for 5% f-MWNT) and shows a very low percolation threshold (0.36% w/w at 30 °C). Analysis of the conductivity data yields the magnitude of percolation exponent 2.1, suggesting three-dimensional percolation is a suitable model for the conduction of the composites. The temperature variation of the conductivity suggests that the conduction might occur through a temperature fluctuation induced tunnelling mechanism. The I-V characteristic curves indicate the semiconducting nature of the composites.