Visualization of on-surface ethylene polymerization through ethylene insertion

Abstract

Polyethylene production through catalytic ethylene polymerization is one of the most common processes in the chemical industry. The popular Cossee-Arlman mechanism hypothesizes that the ethylene be directly inserted into the metal–carbon bond during chain growth, which has been awaiting microscopic and spatiotemporal experimental confirmation. Here, we report an in situ visualization of ethylene polymerization by scanning tunneling microscopy on a carburized iron single-crystal surface. We observed that ethylene polymerization proceeds on a specific triangular iron site at the boundary between two carbide domains. Without an activator, an intermediate, attributed to surface-anchored ethylidene (CHCH 3 ), serves as the chain initiator (self-initiation), which subsequently grows by ethylene insertion. Our finding provides direct experimental evidence of the ethylene polymerization pathway at the molecular level.

Caught in Action: Visualizing Dynamic Nanostructures Within Supramolecular Systems Chemistry

“…Copyright 2018 AAAS; (d) reference [64]. Copyright 2020 ACS; (g) reference [67]. Copyright 2022 AAAS.…”

“…[66] iii) Scanning tunneling microscopy (STM) has been used to image nanostructures with molecular level resolution. In recent times, STM was used for real-time visualization of dynamic processes like catalytic ethylene polymerization (Figure 6g) [67] and nucleation-elongation of two-dimensional dynamic covalent polymerization in ambient conditions. [68] These measurements are currently performed at the solidliquid interfaces and thus limit their use for imaging dynamic processes in bulk solutions.…”

Quantitatively Determining Surface–Adsorbate Properties from Vibrational Spectroscopy with Interpretable Machine Learning

“…The macroscopic performance of all materials is dictated by their microscopic properties. In surface science, surface–adsorbate interaction properties, such as adsorption energy, bond energy, and charge transfer, are closely related to surface molecule recognition, catalytic activity, electrochemistry, etc. − However, obtaining key microscopic properties is rarely straightforward. Often people use spectroscopic tools to first identify material structures and then infer properties of interest.…”

Insights into the Polymerization Reactions on Solid Surfaces Provided by Scanning Tunneling Microscopy

“…3 In combination with polymer chemistry, on-surface polymerization of 1D linear chains and 2D networks has attracted increasing interest and served as a unique platform to generate new polymers and to provide new insights into traditional polymerization reactions. 4 Various classical reactions have been proven effective for the preparation of 1D/2D polymers on solid surfaces (as summarized in Figure 1a), such as the Ullmann coupling reaction, 5−7 direct C−H activation coupling of aryls/alkyls, 8,9 ethylene polymerization, 10 alkyne coupling, 11,12 condensation of boronic acids, 13−15 Schiff-base reaction, 16−18 boronate-ester formation reaction, 19−21 etc. Based on these on-surface reactions, many unprecedented polymers with unique structures and properties, which are hard to achieve via gas/ solution/solid polymerization, have been realized on the surface.…”