UC Irvine

Tremendous synthetic advances in the fields of organic and polymer chemistry have created new opportunities to design advanced, new polymeric materials. Empowered with a suite of advanced synthetic tools, researchers have looked to nature for new inspiration in materials design. Nature has provided a near endless stream of ideas to draw upon for new advanced materials. The goal of this dissertation is to use lessons learned from nature to create cutting-edge, advanced polymeric materials that rely on dynamic molecular interactions. The thesis begins, in Chapter 1, with the background of each individual chapter, including both a guiding principle from nature, as well as, examples of selected previously published work in the field.

In Chapter 2, I draw on lessons learned from the human bone to incorporate sacrificial hydrogen bonds into a covalently crosslinked self-healing material. This work addresses the long-standing challenge in the field of self-healing materials by combining robust mechanical and efficient self-healing properties. Specifically, the toughness of the material is increased 7-fold.

In Chapter 3, I draw from the observation that nature displays remarkable ranges in mechanical properties from simple building blocks to create a widely tunable metallopolymer system. Specifically, the mechanical performance of the system is tuned from viscous oils to stiff plastics by careful selection of type and amount of added metal. This behavior is explained via ligand exchange mechanism, where associative and dissociative mechanisms are leveraged to achieve widely different properties.

In Chapter 4, I imitate the mechanical gradients commonly observed in nature that protect biological materials from damage. Through a sophisticated understanding of metal-ligand crosslinks, I develop a novel approach to generating stiffness gradients in polymeric materials. The result is a mechanical gradient that spans over a 200-fold difference in stiffness.

In Chapter 5, I attempt to duplicate the impressive moldability of silicate glass in covalently crosslinked polymer networks. Towards this goal, I have identified the silyl ether motif as a potential key to creating commercially-relevant vitrimer materials. If successful, these vitrimeric materials could replace thermosets in a variety of applications.