Developing methodology for both polymer and small molecule synthesis is tremendously valuable to society, as these methodologies lead to improvements in lifestyle. This can be observed in the fields of olefin polymerizations leading to low-cost plastics, or small molecule methodology allowing the synthesis of novel pharmaceuticals and additives for polymer processing. These chemical transformations have played a large role in the advancement of society.

A methodology that has been of particular interest in recent years is the field of photoredox chemistry, unlocking a variety of new chemical transformations under mild conditions. However, there remains a large area to explore with respect to applying photoredox catalysis towards controlled chain-growth polymerizations. This dissertation's focus is largely upon photoredox-based polymerizations, particularly in the area of atom transfer radical polymerizations (ATRP). Using photoredox chemistry allows an unprecedented level of temporal control over polymerization, and unlocks the ability to use metal-free catalysts to conduct ATRP. Further, metal-free photocatalysts identified for polymerization were also found to be useful for the development of reductive dehalogenations. The oxygen tolerant nature of metal-free ATRP was also examined, and structure-property relationships were explored with respect to the metal-free photocatalyst. Finally, a deeper mechanistic understanding of the system was developed, and used to alter polymerization properties.