Online

Bocanegra, Jessica Leigh

Chemistry

2020

Ph. D.

Foldamers (i.e. polymers which fold into well-defined shapes) are able to imitate arrangements of proteins, nucleic acids, and polysaccharides. However, previously reported foldamers are limiting in their ability to bind a multitude of guests--mainly due to very rigid conformational skeletal structures. Additionally, these structures commonly rely on [pi]-[pi] stacking and hydrogen bonding to dictate their shapes. We now report a helical foldamer that has (i) the capacity to bind selectively around a myriad of molecules while (ii) still embodying a well-defined, synthetically-controlled shape. We were able to create such structures as single-handed helices with chirality-assisted synthesis (CAS, see: Angew. Chem. 2015, 127, 12963-12967), which was implemented for the first time with copper-catalyzed azo-couplings. With their azo-linkages, these foldamers are light-responsive. When exposed to light, they unfold, and upon thermal relaxation return to their original helical structures. Our stimuli responsive foldamer can be used in pertinent applications such as chemical sensing or biotechnology. Considering the precise folding of shape-defined, ladder polymers, we wanted to extend CAS to shape- and sequence-defined polymers. Supramolecular chemists look to understand how proteins function and fold and to use that knowledge to build complex polymers with shape-determined functionality. Despite understanding the properties that dictate protein structure, controlling or predicting protein structure de novo and applying that to synthetic polymers is still a growing area of polymer chemistry. This extension of CAS aims to employ synthetic techniques to create biomimetic macromolecular assemblies by way of strategic placements of metal ions in the system to cause predictable polymer folding. Additionally, computational manipulations can be used to help guide and, ultimately, yield sequence- and shape-defined polymers. Characterization will shed light on the structural properties of the polymers and will be compared to the predicted polymer folding determined by computational analysis. Finally, the successful generation of these polymers will provide a model for designing a catalog of programmable synthetic polymers and macromolecules with hope for biological applications relevant to their shape and sequence.