Master of Science
Workentin, Mark S.
Functional polymers are desirable due to their use in applications such as drug delivery and bioimaging. This work describes the development of a functional polymer template, expanding upon current routes to creating functional polymer libraries. The methodology utilizes a masking-unmasking strategy to protect and then reveal a strained alkyne for the introduction of functional entities via post-polymerization modification.
The synthesis and characterization by high-resolution mass spectrometry as well as 1H NMR, UV-Vis, and FT-IR spectroscopy of a masked strained alkyne monomer is presented. First, the strained alkyne, masked by a cyclopropenone moiety, was synthesized. Next, a norbornene derivative was covalently attached to the masked strained alkyne to make a monomer capable of ring-opening polymerization and post-polymerization functionalization. The polymerization of masked monomer was then performed and characterized by 1H NMR, UV-Vis, and FT-IR spectroscopy which confirmed the retention of the cyclopropenone moiety. The unmasking of strained alkyne polymer via UV light irradiation and modification via strain-promoted azide-alkyne cycloaddition is also presented. The azides introduced included benzyl azide and a Au25 azide nanocluster. The benzyl functionalized polymer was characterized by 1H NMR, UV-Vis, and FT-IR spectroscopy. The Au25 functionalized polymer was characterized by UV-Vis, FT-IR, and X-ray photoelectron spectroscopy.
The amenability of this strategy to both small molecule and more complex azides is displayed. This provides an exciting new route towards post-polymerization modification to yield a library of functional polymers. This strategy also has the potential for applications in photopatterning as the unmasking method has spatiotemporal control.
Summary for Lay Audience
Polymers are materials made of long chains consisting of repeated subunits called monomers. Polymers are made by a process which links monomers together to from these long chains, referred to as polymerization. Polymers in everyday life include plastics such as those used in grocery bags or rubbers such as those used in the making of tires. Functional polymers, a subset of polymer, are desirable because they are capable of function beyond that of the bulk polymer. Their synthesis is often difficult via traditional methods as the desired functionalities that must be incorporated into monomer are often sensitive and do not survive polymerization. Two ways to circumvent this problem include masking the functional group on the monomer during polymerization or introducing the functional group to polymer after polymerization. This work presents a method of producing functional polymers using both beforementioned methods. The monomer masking-unmasking method used involves shining UV light on the polymer to remove the masking group, which leaves as carbon monoxide gas — meaning no purification is required. After unmasking, the method used to introduce functionality to the polymer post-polymerization is both fast and efficient, requiring little purification. Reported herein is a novel monomer, its unique masking/unmasking method, polymerization, and post-polymerization modification to introduce functionality. This novel monomer and subsequent functionalized polymers were characterized using standard techniques such as nuclear magnetic resonance, UV-Visible, and infrared spectroscopy.
Classen, Kyle, "Development of a Route to Functional Polymers via Click Chemistry" (2020). Electronic Thesis and Dissertation Repository. 7421.