Inspired by the adaptable nature of allyl sulfides, this dissertation examines how addition-fragmentation-transfer (AFT) of allyl sulfides can be leveraged to relax stress in polymer coatings, recycle vinyl-derived plastics, and improve fusion bonding between mixed materials. Our approach to designing stress dissipation in polymer coatings involved post-polymerization modification of azlactone-bearing prepolymers to install allyl sulfide linkages which rearrange to relax stress on irradiation. Film relaxation was monitored using a custom-built optical cantilever, which revealed the complete relaxation of residual stress in allyl sulfide containing coatings. In addition to eliminating residual stress and curvature defects in polymer coatings, our work expanded the chemical library of dynamic AFT materials and furthered the field of covalent adaptable networks (CANs) by highlighting synergy between dynamic bonding and coating applications. Motivated to reduce the amount of plastic waste polluting the environment, and recognizing the unique radical rearrangement of allyl sulfides, I developed a cyclic allyl sulfide (CAS) monomer that copolymerizes with an array of vinyl monomers and affords main chain allyl sulfide vii connectivity for closed-loop chemical recycling. Vinyl-derived copolymers with the additive CAS monomer possessed similar thermal properties to their homopolymer counterparts, indicating minimal changes in processability, however, allyl sulfide containing copolymers were able to be broken down by radical scission and reformed by free radical extension. Our method of chemical recycling by chain extension has the benefit of being tailorable with respect to recovery molar mass and can be easily modified to synthesize higher value products, i.e. upcycle. While the capabilities of the cyclic allyl sulfide comonomer additive are unparalleled, a dramatic relationship between molar mass and CAS copolymerization suggested the presence of undesired transfer during polymerization. In efforts to limit undesired transfer by modifying reaction conditions, CAS copolymerization was found to be compatible with atom transfer radical copolymerization, reversible addition fragmentation transfer copolymerization, emulsion copolymerization, and emulsion extension copolymerization. Undesired transfer was ultimately mitigated by non-selective radical compartmentalization in emulsion polymerization to afford high molar mass products with high concentrations of dynamic allyl sulfide linkages. Both the ability to synthesize high molar mass CAS copolymers and CAS copolymers with radically liable end groups, motivated the discovery of unprecedented AFT self-initiation by dithiobenzoate thermolysis and the use of this advancement to enable allyl sulfide exchange during ultrasonic welding as an enhanced joining technique for immiscible polymers.