Reinforcing polymers with nano-scale fillers like clay, carbon nanotubes, graphene and graphene oxide, is a prescription for fabricating low-density nanocomposites with exceptional mechanical properties.<sup> </sup>However, property enhancement is critically dependent on stress transfer from the relatively soft polymer matrix to the stiff reinforcement. The efficacy of stress transfer is, in turn, sensitive to the polymer morphology, the distribution of the filler particles, and ill-defined intermolecular interactions between the particle surface and polymer. To date a haphazard Edisonian approach to reinforcing inherently low-modulus polymers has been pursued by adding nano-scale fillers to melts or solutions of polymers with random coil secondary structures. Consequently, strong nanocomposites remain elusive in part because of incompatibilities between amorphous polymer morphology and filler causing the latter to aggregate; composite fabrication is also impacted by processing difficulties. Using a water-based process, we report that highly reinforced nanocomposite films can be obtained by simply mixing two uniaxial liquid crystalline solutions: (i) a colloidal nematic filler phase comprised of a suspension of aligned clay or graphene oxide (GO) platelets and (ii) a nematic solution of rod-like high-performance aramid polymers. The resulting mixture is a hybrid biaxial nematic phase with a locally stratified supramolecular organization. On drying, the stratified arrangement in the biaxial fluid is compressed into a uniplanar morphology yielding robust, structural nanocomposite films. Our nanocomposites exceed theoretical estimates for storage modulus, tensile strength and elongation at break. The hybrid mesophase route employed in this work yields a uniform dispersion of filler and provides a new design strategy for fabricating structural nanocomposites.

Mixing rods and discs: Strong nanocomposites from aqueous hybrid liquid crystals

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.