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Self-Organized and Cu-Coordinated Surface Linear PolymerizationCNMS Staff Science HighlightwriteQ. Li, J. Owens, C. Han, B. G. Sumpter, W. Lu, J. Bernholc, V. Meunier, P. Maksymovych, M.l Fuentes-Cabrera, M. Pan, Nature Sci. Rep. DOI:10.1038/srep02102.Low-dimensional polymerization can have unexpected and unique products, as well as reaction kinetics highly distinct from the bulk form. Polymerization of technologically relevant phenylacetylene on a copper surface occurs at dramatically lower temperatures than in the bulk and produces a reactive polymerized allene-copper complex. Topological defects and polymerization in such systems can be explored and controlled with single-molecule resolution.Significance and ImpactResearch DetailsExperiments utilize a home-built scanning tunneling microscope, with temperature range 25-300 K.First principles computation of molecular orientation, bonding, and electronic structure.Approach enables opportunities for assembly and polymerization of new molecules beyond existing paradigms .Scientific AchievementWe have demonstrated cryogenic surface-coordinated linear polymerization of phenylacetylene on copper, forming a mesoscale, self-organized circuit-board pattern of 1D polymer that is hybridized with the surface and exhibits unique electronic properties.

a, Top, b, Side views of the calculated relaxed conformation for periodic cis-poly(phenylacetylene)s adsorbed on Cu(100). (cyan: carbon; orange: copper; light gray: hydrogen) c, High resolution STM image (lower panel) and the calculated isosurface plot for a section of the polymerized structure (upper panel). d, circuit board polymer pattern, stars mark points that bias is applied; e shows subsequent depolymerization.

deWork was performed at the CNMS ORNL, North Carolina University, and Rensselaer Polytechnic Institute. Highlight NarrativeWe demonstrate a controllable surface-coordinated linear polymerization of long-chain poly(phenylacetylenyl)s that are self-organized into a circuit-board pattern on a Cu(100) surface. Scanning tunneling microscopy/spectroscopy (STM/S) corroborated by ab initio calculations, reveals the atomistic details of the molecular structure, and provides a clear signature of electronic and vibrational properties of the poly(phenylacetylene)s chains. Notably, the polymerization reaction is confined epitaxially to the copper lattice, despite the over 10% strain along the C-C backbone of the polymer that subsequently renders it metallic. Polymerization and depolymerization reactions can be controlled locally at the nanoscale by using a charged metal tip, a control that opens possibilities for precisely accessing and controlling conjugated chain-growth polymerization at low temperature. Such capabilities may allow bottom-up design and realization of sophisticated architectures for molecular nano-devices.

Reference:Self-Organized and Cu-Coordinated Surface Linear Polymerization, Q. Li1, J. R. Owens4, C. Han2, B. G. Sumpter1,3, W. Lu2,3, J. Bernholc2,3, V. Meunier4,5, P. Maksymovych1, M. Fuentes-Cabrera1,3, M. Pan11Center for Nanophase Materials Sciences, ORNL, 2Center for High Performance Simulation and Department of Physics, NCSU3Computer Science and Mathematics Division, ORNL4Department of Physics, Astronomy, and Applied Physics, Rensselaer Polytechnic Institute5Department of Materials Science and Engineering, Rensselaer Polytechnic InstituteNature Sci. Rep. (DOI: 10.1038/srep02102).

Acknowledgement of Support:This research was conducted at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy. The work at NCSU was supported by DOE grant DE-FG02-98ER45685. The computations were performed using the resources of the CNMS and the National Center for Computational Sciences at Oak Ridge National Laboratory. This research also used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

1Taming Molecules to Assemble into Linear PolymerswriteControlling molecular assembly into desired architectures by strong bonds enables high stability and efficient electron transport, both key challenges for electronic circuits made from individual molecules. This work identifies a new route to assembly that occurs at low temperature, accessible to semiconductor manufacturing, yet produces thin metallic wires one molecule in width. The approach enables opportunities for assembly of different molecules beyond existing paradigms, each with potentially useful applications.

Significance and Impact

Research DetailsAn ORNL-built cryogenic scanning tunneling microscope enables the experiments to observe and control the polymerization reaction with single-molecule resolution. When combined with large computer simulations that provide additional information about molecular orientation, bonding, and electronic structure, a comprehensive understanding of the mechanisms at the molecular level can be obtained. Scientific AchievementSmall molecules deposited on a flat surface have been discovered to produce a large, self-organized circuit-board pattern of polymer lines.

Q. Li, J. Owens, C. Han, B. G. Sumpter, W. Lu, J. Bernholc, V. Meunier, P. Maksymovych, M.l Fuentes-Cabrera, M. Pan, Nature Sci. Rep. DOI:10.1038/srep02102.These microscope images show self-organized, linear polymer chains that are one molecule wide, forming a circuit board pattern. On the bottom right is a model of the molecular assembly determined by computer simulations.

Work was performed at the CNMS ORNL, North Carolina University, and Rensselaer Polytechnic Institute. 2