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Chem Soc Rev View Article Online REVIEW ARTICLE View Journal | View Issue The historical development of mechanochemistry Cite this: Chem. Soc. Rev., 2013, Laszlo Takacs* 42, 7649 This paper reviews the history of mechanochemistry. It begins with prehistoric times, when reactions could be initiated during grinding and rubbing accidentally, and follows the main developments until recent results and current trends. There are very few records on mechanochemistry until the first systematic investigations by Spring and Lea at the end of the 19th century. For the next decades, mechanochemistry developed slowly; minerals, inorganic compounds, and polymers were the main subjects of investigation. The area became more organized in the 1960s, when several large groups were established and the first dedicated conferences were held. Mechanical alloying was invented in 1966 independently and it became a subject of intense research. Interaction between the two topics was established in the 1990s. In recent years, the mechanochemical synthesis of organic compounds was added to the main subjects and the invention of the atomic force microscope provided new ways to manipulate atoms and molecules by direct mechanical action. The theoretical explanation of mechanochemical phenomena is difficult, as the mechanism is system specific and several length and Received 28th October 2012 time scales are involved. Thiessen proposed the first theory, the magma–plasma model, in 1967, and DOI: 10.1039/c2cs35442j deeper insight is being obtained by computer modelling combined with empirical work. Practical applications have been an important motivation throughout the history of mechanochemistry. It is used www.rsc.org/csr alone or in combination with other steps in an increasing number of technologies. Introduction from chemical changes, there is no way to tell when the chemical efficacy of fine grinding was recognized. Nevertheless, Mechanochemistry is concerned with chemical transforma- given the prevalent use of the mortar and pestle, the observa- tions induced by mechanical means, such as compression, tion and deliberate induction of mechanochemical changes shear, or friction. Unintentional chemical reactions accompany were bound to happen eventually. Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. many forms of mechanical action, like grinding, sliding, or plastic While the beginnings of ‘‘inadvertent mechanochemistry’’ deformation, while the deliberate application of mechanical fade into prehistory, the first systematic studies of mechano- energy, typically by means of high-energy ball milling, provides chemical reactions were carried out only at the end of the 19th a method to prepare useful new materials and to improve the century2,3 and speedy advancement was delayed until the 1960s. efficiency of complex processes. The chemical effects of The unifying principles, boundaries, and methodology of mechano- mechanical action are different from the effects of heat, and chemistry are still not fully established. An essential reason for realizing, explaining, and utilizing this fact is an important the late and slow development is the broad variety of areas, such as thread in the history of mechanochemistry. mineralogy, inorganic and organic synthesis, and tribology, where Grinding can be regarded as the first engineering technology mechanochemical questions arise in very different contexts. This and its traditional instrument, the mortar and pestle, was diversity led to much parallel development, and the preferred already used in the stone age.1 As some grinding operations forums for disseminating results also varied widely. The most were surely accompanied by unintended chemical changes, extreme example is the case of mechanical alloying. It there is a reason to claim that practical mechanochemistry was invented in 1966 independently of the rest of mechano- has been with us for a very long time. The first application of chemistry4 and both areas developed without realizing the grinding was to prepare foodstuffs; it was later extended to treat existence of the other for about twenty years, while hundreds other types of materials, such as minerals, paints, and medicines. of papers were published and regular dedicated conferences As it was impossible to distinguish purely physical size reduction were held on both sides. Recent efforts to bring together the different branches of Department of Physics, University of Maryland Baltimore County, Baltimore, MD, mechanochemistry resulted in increasing exchange of ideas, USA. E-mail: [email protected]; Fax: +1-410-455-1072; Tel: +1-410-455-2524 references across formerly unrelated areas and the organization This journal is c The Royal Society of Chemistry 2013 Chem. Soc. Rev., 2013, 42, 7649--7659 7649 View Article Online Review Article Chem Soc Rev of conferences that encompass broader areas of mechano- examples nor references, indicating that this fact was common chemistry and are attended by professionals with very different knowledge, but poorly documented. research backgrounds. Mechanochemistry is becoming a unified M. Carey Lea carried out another incidental experiment area of research, although further efforts are needed to better connecting mechanical action and chemical response in connect the varied subjects within it. The publication of a 1866.9 He showed that it was possible to ‘‘draw’’ developable collection of review articles by RSC Publishing is a valuable patterns on a sensitized photographic plate with pressure from step in this direction. the rounded end of a glass rod, just as it was possible to imprint The following paper explores the history of mechanochemistry an image with light. Lea used this result to argue that the from the earliest times to the most important current trends. nature of the latent image had to be purely physical, as It is not intended to be a critical scientific review, thus the mechanical action certainly could not result in a ‘‘chemical historical role of a publication is considered more carefully impression.’’ He changed his opinion later and carried out the than the details of its technical content. first widely known investigations on the use of mechanical action to induce chemical changes.3 The first documented application of mechanical stimulus to The early times induce chemical reactions in organic systems is probably the work of Ling and Baker in 1893.10 They prepared halogen There is no historical or archaeological information on how derivatives of quinhydrone by several methods, including and when the first mechanochemical reactions were initiated. trituration of dry mixtures and trituration in the presence of We can only infer that the use of rubbing and grinding had to water or light petroleum as solvent. They did not cite any earlier result in chemical transformations. Making fire by friction or report on the use of the mortar and pestle for the initiation of by striking iron with a flint are other common processes that chemical reactions. Nevertheless, the matter-of-fact manner in include mechanochemical steps. which they turned to this tool suggests that using the mortar Theophrastus of Eresus, Aristotle’s student and successor at and pestle to effect chemical changes was probably familiar to the helm of the Lyceum, wrote a short booklet titled ‘‘On Stones’’ them also. in about 315 B.C. that is the earliest surviving document related to The first extensive investigations on the chemical effects of chemistry.5 It contains a reference on the reduction of cinnabar to mechanical action were carried out by Walthe`re Spring during mercury by grinding in a copper mortar with a copper pestle. the 1880s in Lie´ge, Belgium and by M. Carey Lea a few years Although this process is clearly mechanochemical according to later in Philadelphia, Pennsylvania. Although their circumstances modern classification, its inclusion in the book of Theophrastus and career paths were very different, they were both withdrawn in certainlydoesnotsuggestthatancient Greeks knowingly prac- their personal relationships and felt the most comfortable in the ticed mechanochemistry. Nevertheless, it demonstrates that the research laboratory. As their investigations mark the beginning of application of the mortar and pestle, and consequently the systematic research in mechanochemistry, it is appropriate to possibility of initiating chemical reactions by grinding, extended describe their life and work in some detail. from grains to inorganic materials rather early. W. Spring was born in 1848 into an intellectual family; Nothing explicit is known about the use of mechano- his father, Antoine Spring, was an eminent professor of phy- chemistry for the next 2000 years. But we do know that grinding siology.11 But Spring was more interested in working with his Published on 23 January 2013. Downloaded by University of California - Los Angeles 24/10/2016 21:16:59. and milling were utilized extensively to process grains, minerals, hands than studying the classics and he performed poorly at building materials, pharmaceuticals, black powder, etc. and school. This caused a rift between him and his father that made those processes were necessarily accompanied by chemical Spring timid and isolated. He took up the study of physics and changes. Also, the mortar and pestle was the standard instru- chemistry at the urging of Jean Stas, a prominent chemist and ment in the laboratory of the alchemist and early chemist, thus close friend of the family. Eventually, he completed

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