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Title: Reversible chemistry to control the synthesis and folding of polymeric materials
Author: Gomez Magenti, Jorge
ISNI:       0000 0004 8501 2675
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2020
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Mimicking Nature's ability to create well-defined functional materials is a major goal in the field of polymer chemistry. Two distinct approaches are explored in this work. Part I of the thesis deals with the templated synthesis of sequence-defined oligomers. The ultimate strategy to synthesize macromolecules that have a specific functionality is the selection and evolution cycle, in which template reactions amplify the most promising sequences. All the work done in the field involve biomolecules or bio-inspired systems but there are not, to the best of our knowledge, examples of purely synthetic oligomers than can undergo efficient supramolecular replication. Covalent duplex formation has risen as a promising alternative in order to ensure template saturation during the templating process. This thesis expands on this strategy. A new molecular system was designed, which comprised phenol and carboxylic acid monomers that could selectively and quantitatively couple to each other, thus ensuring duplex formation. The monomers were linked by Glaser-Hay chemistry. A homodimer and a heterodimer were used as templates to synthesize the complementary partners through a replication cycle. The conditions for the base-pair chemistry and the zip-up reactions were optimized. In an expansion of this strategy, spacer units with symmetrical chemical handles were introduced between the template and daughter strand. This helped achieve the replication of two homodimers in a single cycle. Part II of the thesis explores the synthesis of materials making use of living polymerizations and subsequent post-functionalizations in order to obtain systems that fold on themselves, forming polymer nanoparticles. This process is reminiscent of the folding of proteins to form three-dimensional tertiary structures. Since protein functionality is derived from this precise folding of the backbone into a well-defined structure, it would be of great interest to achieve control over the folding of a synthetic polymer. Benzene-1,3,5-tricarboxamide (BTA) and solubilizing units were grafted onto a polycarbonate backbone and the folding behavior of this system was investigated by circular dichroism (CD). In another part of this work, a polyacrylate chain was functionalized with a proportion of permanently anchored BTAs, and with some which were dynamically attached via thermally reversible Diels-Alder adducts. We varied the environmental parameters of the reversible reaction. We propose that this led to the anchoring position of the dynamically-attached BTA adapting to reach a more thermodynamically stable structure. CD measurements of the system were performed to investigate polymer folding as a result of environmental molecular adaptation.
Supervisor: Hunter, Chris Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: template ; replication ; oligomers ; polymer nanoparticles ; adaptation