Mechanical properties of nanoparticle reinforced polymer composites are essential to numerous structural applications. In this work, hierarchical fiber structures are investigated for their beneficial effects on controlling the conformation of 2-D graphene nanoplatelets (GnPs) and 1-D carbon nanotubes (CNTs) through core-shell and periodic lamellae structures. Using an in-house designed spinneret and dry-jet-wet spinning, tri-axial fiber with distinct polyvinyl alcohol (PVA)/GNPs/PVA layers led to a highly-oriented and evenly-distributed GNPs middle layer as a result of molecular chain-assisted interfacial exfoliations between the outer and core polymer layers (Figure 1a). The resulting fiber shows a 73.5% increase in Young’s modulus (~38 GPa), as compared to the pure PVA fiber, and electrical conductivity of 0.38 S m<sup>-1</sup>. By further utilizing the forced assembly process, the interfacial area between polymer and polymer/nanoparticle layers are greatly amplified; a polyacrylonitrile (PAN) based fiber (90 µm in diameter) contains 512 alternating layers of PAN and PAN/CNTs (Figure 1b). Each layer’s thickness is controlled during the multiplication process, with resolutions down to the nanometer scale. The introduction of alternating layers facilitates the quality of CNT dispersion due to nanoscale confinement, and at the same time, enhances their orientation due to shear stress generated at each layer interface, characterized through Raman mapping (Figure 1c). The fiber showed a 46.4% increase in modulus and a 39.5% increase in strength compared to a pure PAN fiber. These fiber structures demonstrate enormous potential as reinforcement fillers in cement, wind turbine, aerospace and automobile industries.

Interfacial interaction assisted nanoparticle orientation control in polymer nanocomposite fibers

ACS Spring Meeting 2021

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