In an effort to synthesize novel carbon-based materials with various dimensionality and hybridization, success has been limited with only diamond, graphite, fullerenes and being a select few that exist in crystalline states as a discrete material. Among these predicted solids, one-dimensional sp3 carbon nanomaterials offer much intrigue due to their structural organization with a diamond-like tetrahedral core that foreshadows the promise of novel mechanical, thermal and optical properties. These sp3 carbon nanothreads live at the juncture of crystalline rigidity and polymeric flexibility. They were first synthesized from the slow, room-temperature compression and decompression of benzene or other small aromatics. However, limited long-range order along the thread axis and inter-thread registry was observed in the maiden synthesis of benzene-derived carbon nanothread. Here we investigate the phase behavior of thiophene up to 35 GPa and establish a pressure-induced phase transition sequence that mirrors previous observations in low-temperature studies. Slow compression to 35 GPa results in the formation of a recoverable saturated product with a 2D monoclinic diffraction pattern along (0001) that agrees closely with atomistic simulations for single crystals of thiophene-derived nanothreads. Paradoxically, this lower-symmetry packing signals a higher degree of structural order, since it must arise from constituents with a consistent azimuthal orientation about their shared axis that is preserved over long axial distances. The simplicity of thiophene reaction pathways (with only four carbon atoms per ring) apparently yields the first nanothreads with orientational order, a striking outcome considering that a single point defect in a 1D system can disrupt long-range structural order. Orientational order of thiophene-derived nanothreads, in the face of sensitivity of 1D systems to structural disruption through defects, encourages efforts towards obtaining higher degrees of synthetic control over nanothread reaction outcomes. The high-pressure synthesis of ordered nanomaterials such as nanothreads can now be extended to aromatic systems with five-membered rings, a further increase in the diversity of compositions and structures achievable.

Evidence of orientational order in thiophene derived carbon nanothreads

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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