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The longest chains of the conductive polymer poly(p-phenylene) (PPP) produced to date are just under one micrometer (thousandth of a millimeter) long – almost an order of magnitude longer than previously possible. A research team from the fields of chemistry and physics led by Prof. Dr. Michael Gottfried from Marburg University, Germany, has now demonstrated for the first time that PPP can be synthesized on surfaces via a specific ring-opening polymerization as genuine chain growth.
The statistically most frequently measured length is around 170 nanometers – with one outlier reaching nearly 1,000 nanometers. A record. The new, halogen-free process does not produce any disruptive by-products, thus opening up a particularly clean approach to ultra-long, conjugated polymer chains. The results have been published by the interdisciplinary team from the Universities of Marburg, Giessen and Leipzig and Chinese researchers in the journal Nature Chemistry (DOI: https://www.nature.com/articles/s41557-026-02092-y).
Targeted chain growth
In contrast to previous surface-based coupling reactions, in which many short molecular fragments come together randomly, here a chain grows in a controlled manner at each end: strained ring molecules are opened by the reactive chain end and attached to the chain. "This mechanism prevents by-products that would otherwise block the surface for further reactions," reports chemist Michael Gottfried. Using high-resolution scanning tunnelling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) with a functionalized tip, the researchers were able to directly visualize individual bonds. X-ray photoelectron spectroscopy (XPS) and NEXAFS measurements additionally confirmed the chemical changes during the reaction. Density functional theory calculations at the University of Leipzig corroborated the proposed reaction pathway and explained the energetic advantages of chain growth. The ultra-long PPP chains can be used to produce novel carbon nanoribbons.
Potential applications for molecular semiconductor devices
The work is basic research in the best sense of the word: it expands the chemical toolkit for producing atomically precise carbon structures – potential building blocks for future molecular electronics, organic transistors or novel semiconductor nanoribbons. "PPP is one of the conjugated polymers whose electronic properties depend heavily on chain length and structural perfection," comments Gottfried. At the same time, the ultra-long chains now available serve as a starting point for defined carbon nanoribbons with tailor-made properties.
Collaboration across short distances
The breakthrough was made possible by the close interaction of chemical design, surface physics, high-resolution microscopy and theory in the LOEWE focus "Principles of On-Surface Synthesis (PriOSS)", a joint project of the Universities of Marburg and Giessen. Short distances, interdisciplinary expertise and the consistent combination of ideas, experiments and atomic imaging – this "Marburg-Giessen spirit" makes it possible to construct molecules as if following a blueprint and to visualize their formation step by step. "The work of Michael Gottfried and his team impressively demonstrates the potential of the close cooperation between the Universities of Marburg and Giessen at the Research Campus of Central Hessen," says Vice-President for Research Prof. Dr. Gert Bange. "The pooling of complementary expertise is leading to scientific breakthroughs and new perspectives for atomically precise materials and future semiconductor technologies."
Prof. Dr. J. Michael Gottfried
Physical Chemistry
Department of Chemistry
Marburg University
Phone.: 06421 28-22541
Mail: michael.gottfried@chemie.uni-marburg.de
Qitang Fan, J. Michael Gottfried et al., On-Surface Radical Ring-Opening Polymerisation Produces Ultra-Long Poly(p-phenylene) for Access to Nonbenzenoid Carbon Nanoribbons, Nature Chemistry (2026) https://www.nature.com/articles/s41557-026-02092-y
The illustration shows how ring-shaped molecules become long chains of a conductive polymer.
Source: Qitang Fan
Copyright: Qitang Fan
Chemist Prof. Dr. J. Michael Gottfried
Source: Jan Hosan
Copyright: Jan Hosan
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