High-Pressure Synthesis of Carbon Nanothreads from Polycyclic Aromatic Hydrocarbons

Carbon nanothreads are one-dimensional sp3-hybridized polymers that have been theorized to exhibit new mechanical, thermal, or electronic properties. When derived from polycyclic aromatic hydrocarbons, nanothreads with thicker diameters emerge, which may promote higher ultimate strengths and/or bending moduli. In this contribution, we investigate the thermally mediated polymerization of naphthalene and pyrene under uniaxial pressure. Both PAHs undergo successful polymerizations, affording crystalline solids with distinctly different interplanar spacings (dNap = 7.77, 6.64, and 6.24 Å; dPy = 8.81, 8.37, and 7.33 Å). The application of heat resulted in the reduction of maximum pressures (at least 8 GPa for naphthalene and at least 4 GPa for pyrene), with a more well-defined diffraction pattern being obtained in the polymerization of pyrene. Spectroscopic analysis supported the formation of predominantly C(sp3)-hybridized extended carbon materials, consistent with simulated crystalline nanothreads without cross-linking.