Photocatalytic Polymer Brush Functionalized Glass Beads for Enhanced Heterogeneous Photocatalysis
Restricted (Penn State Only)
- Author:
- Bell, Kirsten
- Graduate Program:
- Chemical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 28, 2023
- Committee Members:
- Robert Hickey, Outside Unit & Field Member
Bryan Vogt, Major Field Member
Robert Rioux, Major Field Member
Christian Pester, Chair & Dissertation Advisor
Seong Kim, Professor in Charge/Director of Graduate Studies - Keywords:
- photocatalysis
photocatalysts
heterogeneous
polymerizations
controlled radical polymerizations - Abstract:
- Photocatalysis uses readily available light as a renewable energy source to perform a plethora of organic and polymer chemistries, while not requiring high temperatures or pressures. However, many reported light-mediated transformations use homogeneous catalysis approaches, which invariably entails a potential for catalyst contamination. This can lead to discoloration or degradation of synthetic products. Heterogeneous photocatalysis is a viable alternative to reuse catalysts, mitigate catalyst impurities, and improve both sustainability and cost-effectiveness. Recent studies on heterogeneous photocatalytic systems focus on nanoparticles, polymer networks, and metal organic frameworks (MOFs). While each of these approaches introduces their own advantages and challenges, they all have one in common: complex cleaning and recovery processes. This dissertation focuses on the development of a micron-size heterogeneous photocatalyst platform to facilitate the separation process after photocatalysis through simple filtration. Inspired by recent advances in photoredox active polymers and their studies demonstrating the success of functional polymers, the concept transpired to create an effective photocatalyst that can be recycled for multiple uses. The inherent nature of polymer brushes permits the ability for a tunable heterogeneous catalyst. By modifying the polymer brush chemistry, the chemical environment surrounding the photocatalyst can be tailored to enhance interactions during the photoredox process. Variables interrogated in the following work include degrees of photocatalyst incorporation, polymer brush thickness, stability against hydrolysis, and influence of different comonomers and reaction media. The catalytic efficiency is explored through numerous organic reactions and polymer syntheses, such as radical dehalogenations, reversible-deactivation radical polymerizations, and degradation of organic pollutants found in wastewater streams. Recyclability is considered throughout to demonstrate a robust and practically feasible heterogeneous photocatalyst. This user- and eco-friendly approach stands to enhance the ability for scale-up production for heterogeneous photocatalysis. The fundamental research established provides a recyclable photocatalytic platform that can be readily adopted to incorporate other photocatalysts and afford tailoring to other solvents. As such, this concept can transcend beyond the micron-scale supports and advance the fields of macromolecular and photoredox chemistry in their entirety by enabling adaptation of further robust heterogeneous catalysts.