Developing a Robust and Versatile Toolbox for Light Mediated RAFT Polymerization

摘要

Recent efforts focusing on green chemistry have led to a push towards solar energy driven chemical reactions. As part of growing initiatives in reducing carbon footprint, photoredox catalysis under visible light has been receiving much attention in small molecule as well as polymer synthesis. For instance, recent ventures in the field of reversible deactivation radical polymerization (RDRP) are focused on developing novel polymerization methods mediated by visible light. These developments are able to address current limitations of thermal polymerization which includes high energy and temperature initiations, lack of temporal control, poor livingness for “less activated monomers”, restricted stereocontrol, and inability to introduce multiple stimuli to regulate polymerization. As visible light is an abundant, non-invasive, and environmentally benign source, it can act as an external stimulus for the reversible activation and deactivation of various RDRP techniques. In addition, the simple and facile setup of light mediated polymerization enables polymer synthesis to be conducted at ambient conditions without the need for elevated temperatures. This dissertation highlights the development of a robust and versatile toolbox for visible light mediated polymerization, namely Photoinduced Electron/Energy Transfer - Reversible Addition Fragmentation Chain Transfer (PET-RAFT), which caters to highlight the shortcomings of current thermal polymerization techniques. Several areas in polymer chemistry where thermal polymerization approach is deemed severely limited are visited to provide an efficient, alternative approach through implementation of visible light polymerization. The overarching goal of this thesis is to showcase the development of a toolbox of energy efficient polymerization techniques driven by visible light with the ability to provide stereo and temporal control, oxygen tolerance, and versatility to polymerization of different monomer functionalities with various RAFT agents. In addition, this toolbox also capitalizes on the penetration depths provided by long wavelength irradiation sources, such as far red and near infrared sources, to enable low energy polymerization. In short, this thesis provides an access to a toolbox of techniques for visible light polymerization with RAFT that offers to overcome the current limitations of thermal polymerization.