Date of Award

2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Severin T. Schneebeli

Abstract

Finding sustainable ways to create complex, sequence-defined polymers is

essential for future advances in the fields of medicine, electronics, and energy. Thus,

inspired by how nature builds functional macromolecules, this account aims to discover

catalysts, which will facilitate the accurate replication of synthetic nanoscale structures. In

this regard, the comprehensive sight of the work described within this dissertation is to

resolve the following fundamental questions: i) How to generate large, preorganized

macromolecules which can behave as supramolecular hosts to tune the properties of

molecules present in the vicinity of them? ii) What shapes do sequence-defined

oligomers/polymers adopt in solution under various conditions? In what ways can local

polymer conformations be manipulated by binding to supramolecular hosts? iii) Can we

exploit the folding behavior of these polymers as a powerful tool to provide selective

reactivity at the nanoscale and enhance the replication accuracy? Various synthetic

approaches leading to the successful precise manufacturing of synthetic macromolecules

including molecular strips, large macrocycles and porous cages are described. A significant

portion of my PhD research was also focused on the framework of selective catalysis for

polymers functionalization and replication; a unique concept which hasn’t been reported

previously.

Selective catalysis at the molecular scale represents a cornerstone of chemical

synthesis. However, it still remains an open question how to elevate tunable catalysis to

larger length-scales, where nanoscale structures (e.g. whole polymer chains) act as the

substrates and get functionalized in a selective manner. The efficient synthesis of a

hydrazone-linked tetrahedron with large opening, which acts as a catalyst to sizeselectively

functionalize polydisperse polymer-mixtures is described in details.

Experimental and computational evidence are provided to support a dual catalytic effect

exerted by the molecular tetrahedron, which (i) helps to unfold the polymer substrates and

(ii) exposes the amino groups on the polymeric side chains to the 12 triglyme units of the

tetrahedron to accelerate aminolysis. I was able to demonstrate complete reversal of the

intrinsic size-selectivity for polymer functionalization with our tetrahedral cage as the

catalyst. This finding enable the possibility to engineer hydrolytically stable molecular

polyhedra as organocatalysts for size- and future site-selective, post-synthetic polymer

modification (inspired by post-translational protein modification).

Language

en

Number of Pages

220 p.

Available for download on Friday, December 10, 2021

Included in

Chemistry Commons

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