Engineering the Interphase of Single Wall Carbon Nanotubes/Polyacrylonitrile Nanocomposite Fibers with Poly(methyl methacrylate) and Its Effect on Filler Dispersion, Filler-Matrix Interactions, and Tensile Properties

Mechanical reinforcement of polymer nanocomposites with pristine single wall carbon nanotubes (SWNTs) beyond 1 wt % loading is challenging because SWNT-SWNT contacts generate filler aggregation and reduce polymer-filler interaction. Furthermore, SWNTs cannot be covalently functionalized without affecting their inherent properties. In this study, filler individualization and filler-matrix interactions were tuned by helically wrapping the SWNTs with poly(methyl methacrylate) (PMMA), a noncovalent method, and also by changing the PMMA molecular weight. Polyacrylonitrile nanocomposite fibers were produced by dry-jet wet spinning using 1 and 5 wt % PMMA-wrapped SWNTs. Improvement in the filler dispersion and the fiber mechanical properties upon using PMMA-wrapped SWNTs, as compared to SWNTs without PMMA-wrapping, is reported. It is demonstrated that PMMA-wrapping becomes part of the filler-matrix interphase. Increasing the molecular weight of the PMMA wrapping improves SWNT individualization but appears to reduce filler-matrix interaction. Relatively high fiber mechanical properties were obtained when SWNTs wrapped with relatively low molecular weight (15000 g/mol) PMMA were used. Potential applications of these fibers have been discussed.