Asymmetrically functionalized CNTs: preparation of polymer nanocomposites and investigation of interfacial properties

Thanks to their exceptional mechanical strength, carbon nanotubes (CNTs) have been used as nanobridges to improve the compatibility of immiscible polymers. In this study, a novel functionalization was used to preferentially localize CNTs at the interface. The asymmetric functionalization was confirmed by EDX spectroscopy, contact angle measurements, and zeta potential of the CNT array surfaces. The asymmetrically functionalized CNTs (A-CNTs) were then sonicated and added to the polyvinyl alcohol (PVA) polymer and PVA/ low-density polypropylene (LDPE) blends and to compare with the untreated CNTs (P-CNTs) and the symmetrically functionalized CNTs (S-CNTs). The results of FESEM, contact angle measurements and electrical conductivity of PVA/CNTs showed that the A-CNTs were localized at the PVA/air interface, which could mean the CNT tips were oxidized. The tensile test showed that the sequence of tensile strength of the composites was A-CNTs/PVA/LDPE > S-CNT/PVA/LDPE > P-CNTs/PVA/LDPE. The tensile strength of the PVA/LDPE blend could be increased twice and four times more with A-CNTs than with S-CNTs and P-CNTs, respectively, indicating that the A-CNTs promoted the interfacial adhesion between PVA and LDPE blend more.