The properties of molecules, polymers, and solids are determined by their composition and structural and bonding arrangements. The interesting properties of extended carbon solids and molecules arise from carbon-carbon bonding which extends over 6 Å or more in multiple dimensions and can give them great rigidity. Although sp3 nanothreads and sp2 nanotubes are both 1D carbon materials, their properties can be expected to contrast as sharply as diamond and graphite. For example, nanothreads spontaneously self-assemble in the solid state into single crystals hundreds of microns across. The hybrid molecule/nanomaterial nature of nanothreads as hydrocarbons makes them arguably much more chemically versatile. From a traditional polymer perspective, saturated nanothreads are very rigid with a persistence length on the order of 130 nm (vs. a few nm for typical polymers), but in comparison with carbon nanotubes (persistence length of microns) and bulk solids, they are highly flexible. Unique (nano)mechanical properties can be anticipated for this ‘flexible diamond.’ Their stiffness should allow them to precisely orient molecular function on their exterior and heteroatoms in their interior relative to each other, while they are flexible enough to incorporate into cell interiors. Their ability to exfoliate suggests that they could be separated into individual nanothreads with diameters of 6 to 10 Å, making their precisely oriented surface functions readily available to a surrounding chemical environment for further functionalization. Precise orientation of functional groups enables control of self-assembly in a way that is difficult to with flexible polymers. Fully saturated degree-6 nanothreads could have the highest strength-to-weight ratio known and also exhibit a unique combination of strength, flexibility, and resilience.
Nanothreads fill in the last remaining entry in a matrix of the hybridization and dimensionality of extended carbon solids and nanomaterials. Their 1D sp³ bonding should make their properties as different from 1D sp² bonded nanotubes as diamond is different from graphite.
The properties of nanothreads have been the subject of an extensive literature of investigation by theoreticians. Much of this literature regards the mechanical properties arising from their cage-like sp3 bonding, but other properties associated with changes in composition and structure have also been investigated. A listing of the relevant literature is at the end of this page.
We have also synthesized partially unsaturated degree-4 benzene nanothreads, whose rigid backbones hold nearby π orbitals in geometric relationships not seen in traditional organic conductors; these novel forms of π overlap, in a system potentially close to an sp2/sp3 transition, could show unusually strong electron-phonon coupling (and possibly superconductivity), new prospects for organic conductors, and unusual optical and optoelectronic response, especially considering the high degree of order possible in nanothread crystalline packing.
Experimental papers are bolded.
Silveira, J. F. R. V., Muniz, A. R. Diamond nanothread-based 2D and 3D materials: Diamond nanomeshes and nanofoams Carbon 139, 789-800 (2018).
Chen, M. M., Xiao, J., Cao, C., Zhang, D., Cui, L. L., Xu, X. M., Long, M. Q. Theoretical prediction electronic properties of Group-IV diamond nanothreads Aip Advances 8, 075107 (2018).
Wang, T., Duan, P., Xu, E.-S., Vermilyea, B., Chen, B., Li, X., Badding, J. V., Schmidt-Rohr, K., Crespi, V. H. Constraining Carbon Nanothread Structures by Experimental and Calculated Nuclear Magnetic Resonance Spectra Nano Letters, DOI:10.1021/acs.nanolett.8b01736 (2018).
Nobrega, M. M., Teixeira-Neto, E., Cairns, A. B., Temperini, M. L. A., Bini, R. One-dimensional diamondoid polyaniline-like nanothreads from compressed crystal aniline Chemical Science 9, 254-260 (2018).
H. Zhan, G. Zhang, V.B.C. Tan, Y. Cheng, J.M. Bell, Y.-W. Zhang, & Y. Gu, "Diamond Nanothread as a New Reinforcement for Nanocomposites". Advanced Functional Materials, n/a-n/a (2016) http://dx.doi.org/10.1002/adfm.201600119.
Contreras, M. L., Villarroel, I., Rozas, R. How structural parameters affect the reactivity of saturated and non-saturated nitrogen-doped single-walled carbon nanotubes of different chiralities: a density functional theory approach Structural Chemistry 26, 761-771 (2015).
B. Maryasin, M. Olbrich, D. Trauner, & C. Ochsenfeld, "Calculated Nuclear Magnetic Resonance Spectra of Polytwistane and Related Hydrocarbon Nanorods". J Chem Theory Comput 11 (3), 1020-1026 (2015) http://dx.doi.org/10.1021/ct5011505.
Contreras, M. L., Cortes-Arriagada, D., Villarroel, I., Alvarez, J., Rozas, R. Evaluating the hydrogen chemisorption and physisorption energies for nitrogen-containing single-walled carbon nanotubes with different chiralities: a density functional theory study Structural Chemistry 25, 1045-1056 (2014).
M. Olbrich, P. Mayer, & D. Trauner, "A Step toward Polytwistane: Synthesis and Characterization of C-2-Symmetric Tritwistane". Org Biomol Chem 12 (1), 108-112 (2014) http://dx.doi.org/10.1039/c3ob42152j.
D. Wen, R. Hoffmann, & N.W. Ashcroft, "Benzene under High Pressure: A Story of Molecular Crystals Transforming to Saturated Networks, with a Possible Intermediate Metallic Phase". J Am Chem Soc 133 (23), 9023-9035 (2011) http://dx.doi.org/10.1021/ja201786y.
Contreras, M. L., Avila, D., Alvarez, J., Rozas, R. Exploring the structural and electronic properties of nitrogen-containing exohydrogenated carbon nanotubes: a quantum chemistry study Structural Chemistry 21, 573-581 (2010).