Abstract
The ability to bias chemical reaction pathways is a fundamental goal for chemists and material scientists to produce innovative materials. Recently, two-dimensional materials have emerged as potential platforms for exploring novel mechanically activated chemical reactions. Here we report a mechanochemical phenomenon in graphene oxide membranes, covalent epoxide-to-ether functional group transformations that deviate from epoxide ring-opening reactions, discovered through nanomechanical experiments and density functional-based tight binding calculations. These mechanochemical transformations in a two-dimensional system are directionally dependent, and confer pronounced plasticity and damage tolerance to graphene oxide monolayers. Additional experiments on chemically modified graphene oxide membranes, with ring-opened epoxide groups, verify this unique deformation mechanism. These studies establish graphene oxide as a two-dimensional building block with highly tuneable mechanical properties for the design of high-performance nanocomposites, and stimulate the discovery of new bond-selective chemical transformations in two-dimensional materials.
Highlights
The ability to bias chemical reaction pathways is a fundamental goal for chemists and material scientists to produce innovative materials
The graphene oxide (GO) nanosheets used in this work were synthesized using a modified Hummers method[7], and are extensively functionalized with epoxide groups based on X-ray photoelectron spectroscopy (XPS) analysis (Fig. 1a; see Supplementary Table 1)
To explore the origin of the experimentally observed plasticity, we modelled the tensioning of graphene and GO through a series of semi-empirical density functional-based tight-binding (DFTB) calculations using the open-source code CP2K
Summary
The ability to bias chemical reaction pathways is a fundamental goal for chemists and material scientists to produce innovative materials. While defect-free graphene exhibits brittle failure, the cyclic epoxide groups on GO help to dissipate strain energy and hinder crack propagation through a novel epoxide-to-ether transformation, making it ductile This chemically induced plasticity in GO is verified through membrane deflection experiments and rationalized by density functional-based tight-binding (DFTB) calculations. These findings reveal a unique relationship between the chemical structures and mechanical properties of GO at the atomic level, and demonstrate an example of mechanically activated, covalent bond-selective chemistry of the epoxide groups that completely differ from its classical type of ringopening reactions
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