Semester of Graduation

Fall 2021

Degree

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Department

Chemistry

Document Type

Thesis

Abstract

Poly-peptoid based nanoparticles have gained much attention concerning applications in biotechnology or biomedicine due to their biocompatibility and biodegradability. However, the controlled growth of colloidally stable polypeptoid nanostructures of uniform size and controlled geometry remains a major challenge. In this study, the crystallization driven self-assembly (CDSA) of amphiphilic polypeptoid diblock co-polymers, namely poly (N-methyl glycine)-b-poly (N-decyl glycine) (PNMG-b-PNDG), was investigated for the growth of one-dimensional (1D) nanostructures in solution. PNMG-b-PNDG block copolymers (M98D20) were synthesized by sequential benzyl amine-initiated ring-opening polymerizations of the corresponding N-substituted glycine derived N-carboxy anhydrides, in which the degree of polymerization of each block was varied. My efforts have been focused on investigating the seeded growth of the M98D20 polypeptoid block copolymers towards the formation of 1D nanostructures in solution and interrogating the effect of temperature and solvent in the controlled growth of the 1D nanostructures. It was found that in the methanol solvent, M98D20 polymer can be molecularly dissolved, and self-nucleation can be inhibited relative to the seeded growth event. This resulted in controlled elongation of the 1D fibrillar nanostructure where the length of the nanostructure was found to increase proportionally with increasing unimers-to-seed ratio, while the width and height of the nanostructures did not change, which strongly indicates a controlled 1D growth process. Unimer concentration and temperature were also shown to play an important role in the controlled 1D growth of the fibrillar nanostructures likely by affecting the relative rate of the seeded-growth process and dissolution of the seeds. It was found that CDSA growth of the M98D20 polymer at 250C in MeOH afforded 1D nanostructures whose length most closely agrees with the theoretical values based on a living supramolecular polymerization. Future work will also be focused on investigating how to control the CDSA processes to access 2D polypeptoid nanostructures with controlled dimension. The ability to efficiently control the growth of 1D and 2D nanostructures from synthetic polymers by spontaneous assembly will inspire new generations of bioinspired nanomaterials for a variety of potential applications in biomedicine and nanotechnology.

Committee Chair

Donghui Zhang

Available for download on Sunday, November 03, 2024

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