Over the last century, synthetic polymers have become highly abundant in everyday life and have therefore drastically changed the way we live. Due to the need for intricate polymer architectures in high-end applications, polymer chemists are posed with the challenge of developing new methods of synthesizing polymers. Specifically, mild polymerization conditions have become increasingly important and the potential to regulate chain growth via external stimuli has recently become a powerful tool for the development of well- defined polymers. Herein, we describe the development of a photocontrolled cationic polymerizations of vinyl ethers (chapter 2 and 5). This method employs unique chain-transfer agents that have the ability to switch between cationic and radical intermediates. We were therefore able to combine our photocontrolled cationic polymerization with photocontrolled radical polymerization in one pot and mediate the two polymerization mechanisms with different light sources to produce vinyl ether-acrylate copolymers (chapter 3). Using a single-electron oxidant rather than photoredox chemistry to mediate cationic polymerization, allowed us to gain absolute control over polymerization mechanism by switching between chemical and photochemical stimuli (chapter 4). Additionally, we describe the development of a novel, organic acid- mediated cationic polymerization, which proceeds under ambient atmosphere while maintaining excellent control. This simple, single-component system enables the polymerization of a large suite of vinyl ethers without the need for rigorous purification or inert atmosphere (chapter 6). Lastly, we take advantage of the living characteristics of anionic polymerization of styrene and create skewed molecular weight distributions (MWD) through temporally-regulated initiation. We demonstrate that the shape of the MWD has a profound influence on material properties by measuring the Young’s Modulus of poly(styrene-block-isoprene) samples with altered polystyrene MWDs (chapter 7).