Event Information
Mechanical Activation in Polymeric Materials: Applications Towards Mechanochemistry and Catalysis
- Abstract:
Mechanical forces have the potential to induce dramatic reactivity, because the forces typical of daily life are (a) many orders of magnitude greater than the forces between atoms in molecules, and (b) directional, in a way that is fundamentally different from the action of conventional stimuli such as heat and light. We propose to harness this macroscopic mechanical force towards two goals; self-repairing materials, and new externally switchable catalysts.
The strategy directed at self-repairing material thus concentrates on mitigating polymer damage propagation via the incorporation of mechanophores - mechanically activated functional groups - into a polymer backbone. The underlying hypothesis is that at areas of highest polymer stress, mechanical activation can (1) relieve local strain, for example through preferential ring opening, and/or (2) mechanically initiate the formation of chemical cross-links to strengthen the site of potential damage. Our initial studies have investigated highly strained rings such as gem-dichlorocyclopropanes and 2,2-paracyclophanes as potential mechanophores. The synthesis and characterization of a UV-active free radical trap is reported and aids in quantifying mechanophore activation versus covalent rupture in polymeric materials.
The second goal, to develop a new class of mechanocatalysts, is centered around the idea of taking advantage of bond deformations in strained materials. Through the introduction of mechanically active transition metal catalysts into polymer backbones, we aim to direct product formation in a force dependent manner. If successful, a new class of stress-responsive organometallic catalysts will be developed whereby selectivity and/or activity will be directly related to the application of an external mechanical force. Preliminary work reported here focuses on the use of a Rh(I) diphosphine complex towards affecting the selectivity in styrene hydroformylation.
Beyond the primary aims of these studies, we expect this research to supplement the current understanding of polymer degradation processes, provide syntheses of novel types of stress-responsive materials, and create new methods of coupling macroscopic forces to molecular activity.
Preliminary Examination Seminar
Student Exams Seminar