Photocatalyzed controlled radical polymerization of vinyl acetate

Poly(vinyl acetate) (PVAc) is a commodity polymer that finds extensive application in adhesives and paints, among others. This thesis focuses on the synthesis of PVAc via photoinduced electron/energy transfer radical addition-fragmentation chain-transfer polymerization (PET-RAFT), a photocatalyzed radical polymerization method that provides polymers with pre-determined molecular weights and narrow molecular weight distribution, under mild reaction conditions. The mechanism of PET-RAFT is based on the excitation of a photocatalyst (PC) under light irradiation. The PC in its excited state can undergo either single electron transfer (SET) or energy transfer (EnT) to a chain transfer agent (CTA). The CTA is the chemical species that both generates the initiating radicals by homolytic cleavage after interacting with the PC, and affords control over the chain growth via a degenerative chain transfer equilibrium. Some CTAs can be dissociated by direct photoexcitation: this alternative mechanism that does not require a PC is termed photoiniferter polymerization. PVAc was polymerized via PET-RAFT using both metal-based and organic PCs and via the photoiniferter mechanism at different wavelengths to compare the performance of the different systems. The kinetics of the different polymerization methods was studied for samples of varying degree of polymerization by size exclusion chromatography (SEC). The impact of chain transfer phenomena on the molar mass and dispersity of PVAc was systematically assessed as a function of the composition of the polymerization mixture and the type of photocatalytic/photoinduced process. In the last part of the project, the synthesis of degradable PVAc was attempted by copolymerization of vinyl acetate with thionocaprolactone-based species via PET-RAFT. Thionocaprolactone undergoes a radical ring opening process introducing degradable thioester linkages within the PVAc backbone.