Nanoscale Dispersions of Polymers: Aramid Nanofibers

Stable dispersions of nanofibers are virtually unknown for synthetic polymers. They can compliment analogous dispersions of inorganic components, such as nanoparticles, nanowires, nanosheets, etc as a fundamental component of a toolset for design of nanostructures and metamaterials via numerous solvent-based processing methods. As such, strong flexible polymeric nanofibers are very desirable for the effective utilization within composites of nanoscale inorganic components such as carbon nanotubes, graphene, and others.  Here stable dispersions of uniform high-aspect-ratio aramid nanofibers (ANFs) with diameters between 3 and 30 nm controlled by the media composition and up to 10 µm in length were successfully obtained. Unlike the traditional approaches based on polymerization of monomers, they are made by controlled dissolution of standard macroscale form of the polymer, i.e. well known Kevlar.   ANFs revealed distinct morphological and spectroscopic features, such as radial breathing modes in Raman scattering, similar to those observed in carbon nanotubes. ANFs were successfully processed into films using layer-by-layer (LBL) assembly. The resultant films were transparent and highly temperature resilient with enhanced mechanical performance making ANF films highly desirable as protective coatings as well as building blocks of other ultrastrong composite materials in place of or in combination with carbon nanotubes.