Professor Roman Boulatov, of the Department of Chemistry at University of Illinois- Urbana-Champaign, is supported by the Organic and Macromolecular Chemistry Program at the National Science Foundation to perform research integrating organic synthesis, kinetic measurements and computations to develop a method to obtain chemomechanical parameters of reactions of diverse functional groups. Such parameters quantify how reaction rates are affected by external mesoscopic forces acting at individual atoms of the reactants. They are required to model the dynamics of processes at scales between 5 nm and 50 nm. At these scales the dynamics is often governed by rearrangements of a few chemical bonds at rates that depend on non-equilibrium interaction among millions of atoms. In this regime, neither the standard chemical kinetics models, nor Newton laws alone are adequate. Within the chemomechanical approach, the dynamics of the whole process is modeled as a small-molecule reaction perturbed by external mechanical forces. This approach provides an opportunity to understand phenomena of intense contemporary interest, such as operation of ATP-synthase, biological motility, degradation of materials under mechanical stress, and tribochemistry. The rational design of stimuli responsive materials and putative molecular mechanical devices and autonomous nanomechanical devices requires quantitative chemomechanical parameters of underlying chemical reactions. The PI's group will develop small (<1 kDa) bifunctional molecules in which photoisomerization of one moiety (actuator) will exert mechanical forces over 1 nN on stereoelectronically diverse functional groups (mechanophores) and non-empirical approaches to integrate mechanical forces into chemical kinetics formalisms.
Broader impacts of this CAREER award lie in the development of a simple, general method to quantify how external mesoscopic force affects rates of diverse chemical reactions. In the course of developing and refining this method the PI's group will obtain atomistic understanding of the effect of a restraining force on quantum yields of photoisomerization and strategies to maximize the yield by synthetic modifications of molecular photoactuators and rate/force relationships for electrocyclic reactions and heterolytic and homolytic scission of the S-S bond under various experimental conditions. The proposed research will facilitate human resource development in Science, Technology, Engineering and Mathematics (STEM) disciplines by involving underserved high-school (HS) students, HS STEM teachers and first-generation undergraduates under the guidance of graduate students, and postdoctoral fellows. Two Programs will be use to accomplish this: - STIR (Science Teaching through Integrated Research): an ongoing PI-lead collaboration aimed improving the scientific literacy of rural high school students. STIR integrates elements of NSF Programs such as Research Experience for Teachers (RET), Research Experience for High Schoolers (REHS), and Graduate Teaching Fellows in K-12 Education (GK-12) activities and incorporates peer-mentoring strategies into HS Chemistry teaching. - FIRST (Fostering Independence in Research, Studies and Teaching): a comprehensive initiative aimed at addressing specific needs and challenges faced by first-generation college students at a major research university. The interdisciplinary nature of the project forms an excellent training ground for the future generation of nation's scientists.
1. derived theoretically and validated computationally a simple relationship among restoring forces of various internuclear distances at stationary points on the free energy surface of a macromolecule coupled to a constraining potential. 2. demonstrated a general, quantitatively predictive relationship between a molecular restoring force of a reactive site and its kinetic stability and formulated intuitive rules based on this relationship for usefully accurate predictions of kinetic stabilities of reactive sites in stretched polymers. 3. developed simple macrocyclic molecular architectures to mimic the distribution of forces in a monomer of a stretched macromolecule and to vary such forces in small increments and over a sufficiently large range to observe trends without micromanipulation techniques. 4. demonstrated accurate predictions of chemically-driven micromechanical behavior of individual macromolecules from force-reactivity properties of monomers obtained both from experiment and quantum-chemical calculations. 5. calculated and measured intrinsic force-dependent reactivity of a diverse set of reactive moieties, including monomers whose dissociative stability increases in response to pulling force and which undergo accelerated dissociation orthogonal to the pulling force. 6. articulated strategies to exploit the ideas of intrinsic force-reactivity relationship to create new materials for solar thermal energy storage and molecular photoactuation. 6 PhD students, 26 BS and MSc students and 6 postdocs contributed to this project. The project also supported an outreach program in which 11 high school students from rural Illinois carried out research in my group.
