Understanding the Fundamentals of Mechanochemistry
Mechanochemical reactions are traditionally carried out in solvent-free environments using ball mills. These devices are commonly used to reduce particle size and break down matter by applying mechanical energy. This has led to the widely accepted assumption that it is this same mechanical energy that drives chemical reactions in ball mills—an idea reflected in IUPAC’s definition of mechanochemistry as:
"chemical transformation resulting from the absorption of mechanical energy."
Mecha-NO-chem challenges this definition at its core. Our hypothesis is that many reactions currently described as mechanochemical are not truly driven by mechanical forces. Instead, we propose that these are conventional chemical reactions—accelerated by efficient mixing and thermal conditions, often occurring at or near room temperature.
To test this hypothesis, we approach the problem from three key angles:
I. Impact of Mechanical Energy
In recent years, many attempts have been made to quantify the mechanical energy input during ball milling using basic kinematic models. However, these approaches have proven limited in their ability to predict or explain mechanochemical reactivity.
II. Impact of Thermal Energy
It has been shown that even small increases in temperature can significantly influence mechanochemical reactivity. In ball mills, however, this effect is difficult to isolate, as frictional heating depends on multiple variables such as ball size, milling frequency, and the properties of the materials involved.
III. Impact of Mixing
The role of mixing in mechanochemical reactions remains largely underexplored. Recent discussions have raised the question of whether these reactions should be understood as homogeneous or heterogeneous processes—a distinction that significantly affects how we interpret their mechanisms.
“MechaNoChem” has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 948521)