Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Chemistry

Supervisor

Gillies, Elizabeth R.

Abstract

Self-immolative polymers (SIPs) are a subclass of degradable polymers that can be triggered to depolymerize when exposed to a specific stimulus. The main advantages of SIPs are the controlled and predictable depolymerization, signal amplification, and tunability of the polymer regarding which stimuli it responds to. The work presented in this thesis details the synthesis, characterization, and applications of two different families SIPs: polycarbamates (PCBs) and polyglyoxylates (PGs). PCBs are known to have depolymerization rates that are sensitive to environmental conditions surrounding them. In efforts to modify the depolymerization, PCB was incorporated into amphiphilic diblock copolymers, first with multi-stimuli-responsive poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). Evaluation of the ultraviolet (UV) light-responsive depolymerization behaviour under different pH and temperature conditions indicated that temperature was determining factor driving increased depolymerization rates. Secondly, PCB was incorporated into a block copolymer with thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm), which responds at lower temperatures than PDMAEMA. However, this system appeared to aggregate irreversibly in solution even at lower temperatures, making it problematic in experiments. PGs are one of the newer classes of SIPs. Previously, many glyoxylate monomers were inaccessible because of problems synthesizing the monomers or achieving large volumes of sufficiently pure monomers for polymerization. Overall, only a few new monomers were successfully polymerized, only yielding lower degrees of polymerization compared to PEtG. To expand the usefulness of this family, previously inaccessible PGs were achieved through a transesterification reaction with PEtG. A family of alkyl PGs and functional PGs were created, with the latter being used in further post-transesterification modification. Combined this work represents a significant advance in the synthesis and applications of SIPs.

Summary for Lay Audience

Self-immolative polymers (SIPs) are a type of degradable polymers that can breakdown into their building blocks when exposed to a small amount of a specific stimuli, that could include pH, light, or heat. When exposed to the specific stimulus, the responsive end-group is cleaved, and the polymer quickly breaks down end-to-end, like beads falling off a string. This thesis investigates two different types of SIPs. The first class of SIP was attached to a water-soluble polymer, to create a polymer with two distinct sections (one water soluble, and one insoluble in water). When the polymer is in water, a ball like structure formed with the insoluble SIP on the inside and the water-soluble portion sticking outside the polymer. The speed of polymer breakdown was monitored at different temperatures and acidities. The second type of SIP was studied to find new ways of creating subclasses of the polymer. There are two methods of forming new polymers. If we think of a polymer as beads on a string we can either create new coloured beads and then put them on the string (referred to as monomer synthesis), or we can take an already existing beaded string and spray paint it to achieve a new colour (referred to as post-polymerization modification). When monomer synthesis failed, new classes of the SIP were achieved through post-polymerization modification, allowing us to achieved previously inaccessible SIPs.

Available for download on Tuesday, August 31, 2021

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