Fundamental and Applied Investigations in Solid-State Polymer Mechanochemistry

Abstract

The translation of mechanical force to specific chemical reactivity within polymeric materials is known as polymer mechanochemistry. While this phenomenon has long been observed in homopolymers, it has recently attracted much interest as researchers have developed systems capable of site-specific activation and defined outputs in response to mechanical inputs. This thesis aims to contribute to the study of polymer mechanochemistry by describing our fundamental and applied investigations in the field, with a particular emphasis on activation in the solid state. Chapter 1 is an introduction to polymer mechanochemistry, beginning with the characteristics and behavior of polymers under applied load, tracing the historical origins and recent developments in the field, and describing the methods with which systems capable of mechanochemical activation are studied. Chapter 2 discusses our work developing a new mode of mechanochemical activation, which we term “flex activation”, in which bond bending motions are the primary geometric deformation responsible for activation. It describes both initial proof-of-concept studies of oxanorbornadiene mechanophores and the extension of this system to robust scaffolds capable of multiple mechanochemical activation cycles. Chapter 3 describes our ongoing efforts in the extension of the flex activation concept to a new mechanophore capable of releasing N-heterocyclic carbenes upon activation. Finally, Chapter 4 introduces the use of 3D printing to fabricate functional materials containing a mechanochemically-active polymer, along with demonstrating the advantages of this method in making prototype force sensors that would be difficult, if not impossible, to fabricate otherwise.