UC Irvine

This dissertation is composed of two main parts. The first half, Chapter 1 through Chapter 3, discusses my efforts to investigate the selectivity and motion of individual molecular catalysts in polymer networks through the use of single-molecule fluorescence microscopy. The second half, Chapter 4 through Chapter 6, discusses my chemical education research for the transition of existing curriculum to Argument-Driven Inquiry. Chapter 1 focuses on the introduction of single-molecule fluorescence microscopy, specifically towards innovation and elucidation of catalyst dynamics, which is relevant to the first half of this dissertation. Superresolution fluorescence microscopy provides a powerful tool to investigate mechanistic questions and reaction dynamics that would otherwise be resolution- or diffraction-limited, providing insight at the nanometer level. An overview of recent applications of single-molecule and subensemble fluorescence microscopy to synthetic applications and catalytic motion-tracking is included herein, providing context for the scholarship in this dissertation. Chapter 2 discusses, for the first time, the selectivity of individual molecular catalysts for two different reactions is imaged in real time at the single-catalyst level. This imaging is achieved through fluorescence microscopy paired with spectral probes that produce a “snapshot” of the instantaneous chemoselectivity of a single catalyst for either a single-chain-elongation or a single-chain-termination event during ruthenium-catalyzed polymerization. Superresolution imaging of multiple selectivity events, each at a different single-molecular ruthenium catalyst, indicates that catalyst selectivity may be unexpectedly spatial- and time-variable. In Chapter 3, the motion of single molecular ruthenium catalysts during and after single turnover events of ring-opening metathesis polymerization is imaged through single-molecule superresolution tracking with positional accuracy of ±32 nm. This tracking is achieved through real-time incorporation of spectrally tagged monomer units into active polymer chains ends during living polymerization; thus, by design, only active-catalyst motion is detected and imaged, without convolution by inactive catalysts. The catalysts show diverse individualistic diffusive behaviors with respect to time that persist for up to 20 s. Such differential motion indicates widely different local catalyst microenvironments during catalytic turnover. These mobility differences are uniquely observable through single-catalyst microscopy and are not measurable through traditional ensemble analytical techniques for characterizing the behavior of molecular catalysts, such as NMR spectroscopy. Traditional laboratory classes are often administered through “cookbook” style curriculum that does not accurately reflect the scientific inquiry and debate. To reflect this more realistic picture of the scientific process, the traditional curriculum of confirmation labs for the lower division undergraduate labs at University of California, Irvine has been adapted to Argument-Driven Inquiry, a guided inquiry curriculum that allows for debate and revision. Chapter 4 introduces a literature overview of the process of Argument-Driven Inquiry and its use as an alternative style of laboratory curriculum in other institutions. Chapter 5 describes the creation of a second quarter of a two-quarter sequence of argument-driven-inquiry general chemistry laboratories. The course contains four projects investigating the chemistry of spices (vanilla, cinnamon, spearmint, and cloves) and incorporates a structured review and hands-on applications of fundamental concepts necessary to transition between general and organic chemistry (colligative properties, TLC, synthesis, characterization tests, and unknown determination). The inquiry-based curriculum was designed to give students increasing responsibility and freedom to develop experimental design skills. Specifications grading is used to increase concept iteration and encourage teamwork amongst students. Survey results for student learning style, feelings about chemistry, and perception of the course format are compared for first and second quarter courses. Changes in survey responses show higher average positive responses in many categories for the second quarter course. Chapter 6 outlines the ongoing effort to design a series of Organic Chemistry experiments to be used in an ADI course, with a focus on designing intentional variation to lead to robust argumentation. These experiments were evaluated by a group of undergraduate beta-testers, who performed the full course as students, including the argumentation sessions. These designed experiments are discussed and analyzed based on student feedback. The argumentation sessions were analyzed by the Assessment of Student Argumentation in the Classroom protocol to quantify the level of discourse achieved by the students. Both results are evaluated to determine the efficacy of the designed curriculum. Future directions and continuing work on the curriculum are outlined.