Effects of ionic liquids and thermal annealing on the rheological behavior and electrical properties of poly(methyl methacrylate)/carbon nanotubes composites

Abstract

Poly (methyl methacrylate)/carbon nanotubes (PMMA/CNTs) composites with varying CNTs concentration were prepared, in which the CNTs were physically modified by two kinds of ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF6]), named B-CNTs and H-CNTs, respectively. The effects of ILs on the dispersion of CNTs and the rheological and electrical properties of PMMA/CNTs composites were investigated. It is demonstrated that the addition of ILs could significantly improve the CNTs dispersion in PMMA matrix, which as a result leads to the decrease of rheological percolation threshold and enhancement of the electrical conductivity of the composites. Compared with PMMA/B-CNTs, more homogeneous dispersion of CNTs, smaller rheological percolation threshold but higher threshold of electrical conductivity percolation could be found in PMMA/H-CNTs composites. The discrepancy between rheological and electrical conductivity percolation threshold could be ascribed to the stronger interaction between [HMIM][PF6] and CNTs than that of [BMIM][PF6] as evidenced by Fourier Transform Infrared (FTIR) results. Thermal annealing could apparently facilitate the electrical conductivity of both PMMA/CNTs and PMMA/B-CNTs but it has no obvious effect on that of PMMA/H-CNTs composites.