(3h) Cycloaddition Polymerizations: New Uses for Old Reactions

Whether the system of interest is a protein or microchip, working on the nanometer scale requires highly efficient and well controlled reactions that can be externally manipulated.  The development of such reactions presents a key opportunity for realizing improved materials and devices.  Cycloaddition reactions such as the Diels–Alder reaction and the copper-catalyzed azide–alkyne cycloaddition (CuAAC reaction) are highly efficient for bond formation and allow selective reactions in the presence of other functional groups.  My work focuses on understanding the relationships between the underlying chemical mechanisms and the resulting material properties.  Moreover, I am interested in novel strategies for remotely triggering these reactions that allow for the creation of self-healing, lithographic, and other functional mateirals.  In one example, I have utilized magnetically susceptible particles to trigger reversible material healing in a Diels-Alder network.  This novel process enables the material to retain its native properties over ten cycles of fracture and repair, demonstrating the Diels–Alder reactions utility for creating a selectively healable material.  In a different, but related example, masked or focused laser light can be used to selectively eliminate the reversibility of the Diels–Alder adducts.  Upon heating depolymerization occurs and the unexposed material can be removed.  Unlike conventional approaches this technique allows for the fabrication of arbitrary three dimensional objects.