Amino-functionalized MWNTs

The surface modification can aim at different goals for example, the purpose could be the achievement of a superior chemical compatibility between the two phases through the addition of bridging agents [82]. The modification of the CNTs surface is frequently reported to increase their affinity with polymer solution. One example has been reported in the literature to obtain MMMs of multiwalled carbon nanotubes (MWNTs) in hydrophilic polymer blends for the synthesis of gas separation membranes. Acidification [62] and amino functionalization [56] of the fillers have been performed to increase their dispersability in an aqueous-based casting solution and to offer a reactive moiety for further crosslinking with polymer chains. 

Recently, Kevlar-functionalized nanotubes were prepared by heating Kevlar with MWNTs in the presence of sulfuric and nitric acids under reflux. This resulted in the partial oxidation and functionalization of CNTs with carboxylic acid groups, which formed hydrogen bonds with amido-groups, as well as terminal carboxylic acid and amino groups in Kevlar. This process produced Kevlar-coated CNTs, which have been utilized for the fabrication of MWNT-polyvinylchloride (PVC) composites. Plasma polymerization treatment enables the coating of CNTs with a very thin (3 nm) polymer layer. Polymer composites based on these coated nanotubes enhanced interfacial bonding in a PS polymer matrix [22, 91]. 

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