The abstract:

The response of polymeric materials to mechanical loads spans orders of magnitude in time and length. At the smallest scale are often dramatic changes in the kinetic stabilities of individual chemical bonds with the resulting changes in bonding patterns and chemical composition of the material altering its properties and ultimately leading to its catastrophic failure.

Prof. Boulatov's group integrates synthesis, measurements, computations and theory to learn how to exploit such load-induced chemistry (1) to understand the response of amorphous polymeric materials to mechanical loads at the atomic level and (2) to create practical strategies for directing energy dissipation pathways during repeated mechanical loadings to obtain useful patterns of material response, including self-healing, actuation and autonomous reporting of local stresses.

In this seminar Prof. Boulatov will:

1. Present the conceptual framework that guides our thinking about coupling between macroscopic loads and localized chemical reactivity in soft materials and explain how the essentially intractable problem of chemical response of such materials to mechanical loads is reduced to a series of manageable questions that address processes at individual lengthscales.

2. describe experimental and computational methodology to obtain correlations between restoring force of an axially strained monomer and its kinetic stability (force-rate correlations).

3. demonstrate how a rate-force correlation of an isolated monomer can be used to predict chemically-driven micromechanical behavior of its polymer.

4. describe examples of monomers whose response to pulling force may contradict our everyday experience, including chemical bonds whose stability against dissociation increases as larger pulling force is exerted on them and monomers which respond to pulling force by fragmenting orthogonal to the force direction.