Structural, Thermodynamic, and Educational Considerations in Self-Assembly.

Self-assembly;Active Learning;Graduate Student Instructor Professional Development;Chemistry;Science;Chemistry

Barnard, Rachel A.Maldonado, Stephen ;

University of Michigan

关键词: Self-assembly;    Active Learning;    Graduate Student Instructor Professional Development;    Chemistry;    Science;    Chemistry;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/108960/racbar_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In molecular self-assembly, both structure and thermodynamics are critical in monolayer formation. The potential for generating complexity in self-assembled system was explored in two dimensions by investigating the two-dimensional crystals formed from a series of multicarboxylated arenes related to trimesic acid at the heptanoic acid/highly ordered pyrolytic graphite interface. In the molecular design strategy for this series, phenylene spacers were added between the central phenylene core and one or more of the carboxylic acids of trimesic acid. By this design strategy, monolayers in multiple plane groups and one example of a disordered phase were obtained for this series. The composition of the dimers in the two-dimensional monolayers mirrors the composition of the carboxylates at metal centers in microporous coordination polymers incorporating these carboxylated arenes as organic linkers suggesting spacers as a promising design tool. To directly explore the thermodynamics of monolayer self-assembly, experimental heats of adsorption from solution onto powdered graphite were measured using flow microcalorimetry for a series of aliphatic adsorbates varying in their terminal functional group. Monolayer structure for each adsorbate is known from the scanning tunneling microscopy literature. Comparing these experimental values to computationally derived lattice energies for this series, the ordering of the enthalpies of adsorption and lattice energies did not match when pre-assembly in solution or strong solvent analyte interactions were not accounted for by the gas-phase, computationally derived lattice energies. Such findings have important implications for systems, such as industrial separations, which rely on selective adsorption from solution. While there are increased calls for more active learning opportunities in post-secondary classrooms, little is known about how to effectively teach active learning strategies. To address this need, a semester long, active learning professional development program was designed for graduate student instructors (GSIs) teaching general chemistry lecture discussion sections to introduce the graduate student instructors to active learning strategies which they would then embed in their discussion sections. The GSIs valued practice in authentic instructor responsibilities and exhibited a range in understanding and implementation of active learning strategies. Long term, ongoing professional development of individuals remains critical in instructional reform.