Intrinsic and Catalyzed Photochemistry of Phenylvinylketone for Wavelength‐Sensitive Controlled Polymerization

Reversible addition‐fragmentation chain transfer (RAFT) photopolymerization of phenylvinylketone (PVK) is investigated. The polymerization is investigated both in the presence of two photocatalysts (iridium tris(phenylpyridine (Ir(ppy)3) and zinc tetraphenylporphyrin (ZnTPP)). The polymerization was efficient in the absence of photocatalyst, and accelerated by Ir(ppy)3, whereas ZnTPP was found to lead to retardation of polymerization. In all cases, well‐controlled polymers were synthesized with linear growth in Mn with conversion and narrow molecular weight distributions. The observed photopolymerization kinetics were consistent with a Norrish Type 1 reaction of PVK to give two radicals. The polymerization kinetics were investigated as a function of wavelength, with the reaction rate being fastest with blue irradiation (440 nm), which is surprisingly far from the absorption maximum of PVK and Ir(ppy)3. Photodegradation of PVK was observed under UV irradiation, but the polymers were stable against visible light. Something for free? A mechanistic study of phenylvinylketone (PVK) photopolymerization reveals the efficient and intrinsic photochemistry of the PVK monomer. Mechanistic studies show that well‐controlled polymers can be generated by RAFT polymerization, with the most efficient polymerization occurring under blue light irradiation. Surprisingly the irradiation wavelength giving the fastest polymerization is red‐shifted from the peak of the UV/Vis absorption spectrum of the photoactive monomer (see picture).