Synergistic effects of two types of ionic liquids on the dispersion of multiwalled carbon nanotubes in ethylene-vinyl acetate elastomer: preparation and characterization of flexible conductive composites

Abstract

Flexible conductive composites based on an elastomer, ethylene-vinyl acetate copolymer (EVM), and multiwalled carbon nanotubes (MWCNTs) were fabricated by melt-blending and subsequent crosslinking. Two types of ionic liquids, tributylmethylammoniu bis(trifluoromethanesulfonyl)imide and 1-ehtyl-3-methylimidazolium tetrafluoroborate, have been used to modify MWCNTs for the purpose to improve the dispersion of MWCNTs in the polymer matrix. It was found that the MWCNTs modified by the individual IL form agglomerates in the EVM matrix, while the MWCNTs modified by the two types of ILs simultaneously disperse in the EVM matrix homogeneously. Moreover, the nanocomposites based the MWCNTs modified by the combination of the two ILs exhibit improved mechanical and electrical properties. The mechanism of such synergistic effects has been investigated. It was found that EVM is miscible with tributylmethylammoniu bis(trifluoromethanesulfonyl)imide and it is immiscible with 1-ehtyl-3-methylimidazolium tetrafluoroborate. On the other hand, MWCNTs show higher interaction with 1-ehtyl-3-methylimidazolium tetrafluoroborate than tributylmethylammoniu bis(trifluoromethanesulfonyl)imide. Therefore, the uniform dispersion of MWCNTs in EVM matrix is attributed to the “bridging” effects by the two ILs due to the different interactions of the two ILs with MWCNTs and EVM. The application by two types of ILs modified MWCNTs in polymer matrix opens a new fabrication strategy for high performance polymer nanocomposites.