PET-RAFT Polymerization: Mechanistic Perspectives for Future Materials.

In the past decade, photochemistry has emerged as a growing area in organic and polymer chemistry. Use of light to drive polymerization has advantages by imparting spatial and temporal control over the reaction. Photoinduced electron/energy transfer reversible addition-fragmentation chain transfer polymerization (PET-RAFT) has emerged as an excellent technique for developing well-defined polymers from a variety of functional monomers. However, the mechanism, of electron versus energy transfer is debated in the literature, with conflicting reports on the underlying process. This perspective focuses on the mechanistic aspects of PET-RAFT, in particular, the electron versus energy transfer pathways. The different mechanisms are evaluated, including evidence for one versus the other mechanisms. The current literature has not reached a consensus across all PET-RAFT processes, but rather, each catalytic system has unique characteristics.

In-situ Chemiluminescence-Driven Reversible Addition-Fragmentation Chain-Transfer Photopolymerization.

The power of chemical light generation (chemiluminescence) is used to drive polymerization reactions. A biphasic reaction is developed such that light-generating reactions are confined to the organic phase and photopolymerization occurs in the aqueous phase. Well-defined RAFT-capped polymers are synthesized and the kinetics are shown to be dictated by light generation.

Rise and Fall: Poly(phenyl vinyl ketone) Photopolymerization and Photodegradation under Visible and UV Radiation.

Vinyl ketone polymers, including phenyl vinyl ketone (PVK), are an important class of polymers due to their ability to degrade upon irradiation with ultraviolet light which makes them useful for a variety of applications. However, traditional radical methods for synthesizing PVK polymers give rise to poor control or are unable to produce block copolymers. This work uses reversible addition-fragmentation chain transfer polymerization (RAFT) and photochemistry to polymerize PVK. When visible blue radiation of 440 ± 10 nm is used as the light source for the photopolymerization, rapid polymerization and well-defined polymers are created. This RAFT method uses PVK as both monomer and radical initiator, exciting the PVK mono-mer by 440 ± 10 nm irradiation to avoid the use of an additional radical initiator. Once the poly-mer is synthesized, it is stable against degradation by blue light (440 ± 10 nm), but upon exposure to ultraviolet (UV) radiation (310 ± 20 nm) significant decrease in molecular weight is observed. The degradation is observed for all poly(PVK) materials synthesized.