Investigations of Disassembling Polymers and Molecular Dynamics Simulations in Molecular Gelation, and Implementation of a Class-Project Centered on Editing Wikipedia.

Abstract

Low molecular weight gelators are molecules that self-assemble to form entangled fibers that entrap solvent through surface tension and capillary forces. The greatest challenge is to design new gelators for specific applications because the impact of structural features on gel formation is unknown. This thesis describes our efforts towards designing new gelator scaffolds via the traditional methods of synthesis and gel screening, and new methods based on computational studies. Chapter 2 describes the synthesis and characterization of aryl trihydroxyborate sodium salt gelators, serendipitously found to form gels in aromatic solvents. We discovered an unusual dependence of the critical gelation concentration on alkyl chain length, highlighting that a number of interactions drive gel formation. Chapter 3 describes the development of computational models to predict gelation ability. Molecular mechanics was used to compare dissolution enthalpies of gelators and nongelators, which were previously shown to be different. Several models were developed, including modeling interactions as a liquid, this did not reproduce experimental observations, suggesting that solid-state interactions that are important in gelation. Chapter 4 describes the synthesis of polymers that disassemble when the end-group is released by an analyte. Several attempts at synthesizing monomers with gelation abilities are described. Overall, these efforts illustrate the challenges of modifying an existing scaffold into a gelator as structural features on gel formation are largely unknown. Chapter 5 presents the design, modification, and implementation of a class project based on editing Wikipedia. Through informal open-response surveys and retrospective panel surveys, the students’ responses indicated that teaching with Wikipedia is and effective method for students to explore advanced topics and learn how to communicate science to a diverse audience. Chapter 6 describes an extension of the original project for use in undergraduate chemistry courses. Analysis on student expectations of learning reveled that the scope of the project, was too broad for the students to recognize the learning goals. Student-led organization centered on editing Wikipedia was developed to keep new editors contributing longer than the average new editor. This is the first example of the development of an internal organization to formally introduce students to Wikipedia’s editing infrastructure.