Dispersions of Aramid Nanofibers: A New Nanoscale Building Block

TLDR

Stable dispersions of synthetic polymer nanofibers are virtually unknown, yet aramid nanofibers could complement inorganic nanomaterials and enable design of nanostructures and metamaterials via solvent‑based processing. Aramid nanofibers are produced by controlled dissolution of Kevlar threads, yielding high‑aspect‑ratio fibers with carbon‑nanotube‑like morphology that can be assembled into transparent films by layer‑by‑layer deposition. The resulting films are transparent, highly temperature‑resilient, and display enhanced mechanical properties, making ANF films desirable as protective coatings, ultrastrong membranes, and high‑performance material building blocks.

Abstract

Stable dispersions of nanofibers are virtually unknown for synthetic polymers. They can complement 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 nanowires, carbon nanotubes, graphene, and others. Here stable dispersions of uniform high-aspect-ratio aramid nanofibers (ANFs) with diameters between 3 and 30 nm 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 aramid polymer, that is, well-known Kevlar threads, and revealed distinct morphological features similar to carbon nanotubes. ANFs are successfully processed into films using layer-by-layer (LBL) assembly as one of the potential methods of preparation of composites from ANFs. The resultant films are transparent and highly temperature resilient. They also display enhanced mechanical characteristics making ANF films highly desirable as protective coatings, ultrastrong membranes, as well as building blocks of other high performance materials in place of or in combination with carbon nanotubes.