Improving the filler dispersion of polychloroprene/carboxylated multi-walled carbon nanotubes composites by non-covalent functionalization of carboxylated ionic liquid

The effect of the non-covalent modification of carboxylated multi-walled carbon nanotubes (MWCNT) by a carboxylated ionic liquid (IL), 1-carboxyethyl-3-methylimidazolium bis(trifluoromethyl sulfony)imide (CMI), on the polymer-filler interactions, filler dispersion, thermal stability, mechanical and dielectric properties of polychloroprene (CR)/MWCNT composites were studied. The better dispersion of MWCNT in CR was attributed to the “cation-π” interaction and π-π stacking between MWCNT and CMI, and other possible intermolecular interactions related to carboxyl groups on MWCNT and CMI. After the introduction of CMI into CR/MWCNT composites, the Payne effect became more pronounced as evidenced by nonlinear viscoelasticity test. After the addition of 16 phr CMI into CR/MWCNT (100/8) composite, the storage modulus greatly increased from 277 MPa to the maximum value of 389 MPa. Meanwhile, the tensile strength increased from 12.5 to 18.2 MPa, and the elongation at break increased from 411% to 464%. This improvement in mechanical properties was accounted from stronger polymer-filler interactions and the plasticizing effect arising from CMI. The presence of CMI ions as permanent dipole and the less possibility for MWCNT to aggregate together gave rise to a big increment in permittivity of CR/MWCNT composites.