Issue Date: November 26, 2012
The extensive article on mechanochemistry omitted seminal, quantitative work by Roman Boulatov, formerly at the University of Illinois, Urbana-Champaign (C&EN, Oct. 1, page 55).
In a comprehensive approach to understand the chemical response of polymers to mechanical loads, Boulatov and colleagues combined theoretical, computational, and experimental studies of “mechanochemistry.” For example, they derived a statistical-mechanics model of reaction kinetics in stretched (macro)molecules (J. Mater. Chem., DOI: 10.1039/c0jm04079g) and used it to demonstrate the importance of hitherto-neglected entropic effects in determining force-dependent reactivity (J. Am. Chem. Soc., DOI: 10.1021/ja207421v). They also demonstrated how the classical Eyring-Bell-Evans model of force-dependent reactivity is a special case of Taylor expansion of the activation energy around a strain-free geometry (Pure Appl. Chem., DOI: 10.1351/pac-con-09-11-36 and 10.1351/pac-con-10-09-33).
Next, Boulatov showed computationally (ChemPhysChem, DOI: 10.1002/cphc.201200207) and theoretically that the kinetic stability of a reactive site in a stretched polymer depends on two factors: the “intrinsic” force sensitivity of the kinetic stability of a reaction and the fraction of the microscopic stretching force that is transmitted to the reactive site. Surprisingly, this is independent of the size or chemical nature of the polymer. These ideas were then used by Stephen L. Craig and colleagues to improve the kinetic stability of functional groups by modifying the inert parts of the polymer (J. Am. Chem. Soc.,DOI: 10.1021/ja302996n).
Boulatov also demonstrated (J. Am. Chem. Soc.,DOI: 10.1021/ja301928d) that the knowledge of the intrinsic force-reactivity correlation of a monomer is sufficient to predict the micromechanical behavior of its polymer, thus enabling accurate predictions of the kinetic stabilities of various monomers in macroscopically loaded polymeric materials before such polymers were synthesized. This work was analyzed in Nature (DOI: 10.1038/487176a).
Finally, Boulatov also developed the sole method to control the local restoring force in reactive moieties and to measure the kinetics of diverse chemical reactions as a function of this local force (Nat. Nanotechnol., DOI: 10.1038/nnano.2009.55; Angew. Chem. Int. Ed., DOI: 10.1002/anie.200990196; J. Phys. Chem. Lett., DOI: 10.1021/jz100878z).
James P. Collman
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