CCI Phase I: NSF Center for the Mechanical Control of Chemistry (CMCC)

A. Center Overview A.1. Center Vision. The Center for the Mechanical Control of Chemistry (CMCC) proposes to advance the field of chemistry by enabling the predictive application of mechanical forces to direct and control chemical reactions. The effects of light, electric charge, and heat on chemical reactivity are well-understood. However, our under-standing of the use of mechanical force to alter reaction energies and pathways is far less developed. As one of the last fundamental fron-tiers in chemistry, force, as a controlling synthetic input, has the po-tential to open new avenues in organic and inorganic synthesis, ca-talysis, and biology.1-6 The CMCC’s vision is to transform the under-standing of mechanically-driven chemistry, enabling the widespread ability to predict, direct, and scale up mechanically-driven reactions. Outcomes of this work will enable more sustainable, efficient, safer, cheaper and more selective chemical syntheses. 7 Mechanical forces have been shown to strongly affect chemical reaction rates, with the kinetics and product distributions sensitive to the input of mechanical energy.1-6 Early experiments focused on un-derstanding polymer degradation under tension, and more recently chemical bond scission by pulling.4-5 New synthetic routes also have been discovered using compression and shear (e.g. via ball and plan-etary milling) for novel chemical syntheses.1 However, these studies show that it is difficult to precisely control or even define the direction of the applied force with respect to the portion of the molecule undergoing a mechanochemical reaction. While more recent work has sought to make these connections,7 we do not yet have the atomistic insights needed to establish predictive relationships between force and reactivity, which ultimately hinders the development of scal-able mechanosyntheses. CMCC overcomes this key knowledge gap by studying reactions on or between well-defined sur-faces, affording control over applied forces and reactant geometries. Our proposed studies will build toward model reactions in real in situ mechanical contacts, including those found in ball milling reac-tors, to reveal fundamental insights into mechanochemical processes, such as bond formation kinetics under applied force, and reaction regio- and stereoselectivities, allowing CMCC to develop new ana-lytical methods, fundamental models, and versatile reactors that enable directed mechanocatalyzed synthesis of organic and inorganic materials.3 CMCC will apply novel experimental (metrology) tools and theoretical concepts to assess the influence of mechanical forces on reaction rates and product selectivities for a set of model systems. A deliverable will be the design of new, scalable mechano-chemical reactors, fulfilling CMCC’s vision of deploying mechanical force as a reliable method for se-lective and sustainable chemical synthesis. A.2. Potential for Transformative Impact in Chemistry. A broad, fundamental understanding of how mechanical forces, acting alone or with other processes (i.e. heat, electric charge, and light), alter the rates and pathways of chemical reactions will be realized through this Center (Fig. 1). CMCC will focus on the effect of compressive and shear forces on reactions given their significant relevance to mechanosynthesis. Our central hypothesis is that a molecular-level understanding of mechanochem-istry will unlock new avenues for chemical reactions, catalysis, and solvent-free synthesis by enabling predictive models for mechano-catalyzed reactions (Phase 1) that will broadly facilitate s