Quasi-isotropic high pressure, large volume synthesis of a polymeric composite incorporating diamond-like carbon nano-threads

The high pressure synthesis of hydrogenated, sp3-hybridized carbon nanothreads from aromatics is a vibrant research area. These nanomaterials are expected to join the high tensile strength of diamond with the high flexibility of polymers. The smart selection of the initial aromatic substance leads to tailor transport and optical properties and to enhance the selectivity of the synthesis. So far, the synthesis has only been performed in two-opposed anvils cells, supporting large uniaxial stress. To increase chemical selectivity and yield, the interplay between this stress and the intrinsic relative molecular orientation in the starting crystal is a very important aspect to clarify. We report the synthesis (30 GPa) of a diphenylacetylene-derived polymeric composite incorporating domains of potentially semiconductive C-nanothreads, performed in a large volume, multi-anvil two-stage press. This device provides quasi-isotropic direct compression of millimeter-sized samples. Materials characterizations were performed by synchrotron, powder X-ray diffraction and Infrared spectroscopy. The product is quite similar to those previously obtained in diamond anvil cells, showing that the synthesis is not related to uniaxial stress and is instead driven by the favourable intermolecular orientation in the initial molecular solid. These findings are very likely to be common to many other aromatic systems, and also show the scalability to large volumes of the C-nanothreads synthesis.