Interlocking Matrix and Filler for Enhanced Individualization and Reinforcement in Polymer-Single-Walled Carbon Nanotube Composites

Poor individualization and interfacial adhesion preventsingle-walledcarbon nanotube (SWNT)-polymer composites from reaching outstandingmechanical properties. With much larger diameters, but common structuralfeatures (high aspect ratio and absence of functional groups for covalentor supramolecular attachment with the polymer), carbon fibers facesimilar problems, which are addressed by covering the fibers witha thin layer of polymer. This sizing strategy has allowed carbon fibersto become the filler of choice for the highest performing materials.Inspired by this, here we investigate the use of the mechanical bondto wrap SWNTs with a layer of polymeric material to produce SWNTsmechanically interlocked with a layer of polymer. We first validatethe formation of mechanically interlocked nanotubes (MINTs) usingmixtures of SWNTs of relatively large average diameter (1.6 & PLUSMN;0.4 nm), which are commercially available at reasonable prices andtherefore could be technologically relevant as polymer fillers. Wethen design and synthesize by ring-opening metathesis polymerization(ROMP) a polymer decorated with multiple U-shaped molecules, whichare later ring-closed around the SWNTs using metathesis. The obtainedhybrids contain a high degree of individualized SWNTs and exhibitsignificantly increased mechanical properties when compared to thematrix polymer. We envision that this strategy could be employed toproduce SWNTs interlocked with polymer layers with various designsfor polymer reinforcement.