Controlled/living radical polymerization of methyl methacrylate using γ-radiation as an initiation source

Mapping Formation Pathways and End Group Patterns of Stimuli-Responsive Polymer Systems via High-Resolution Electrospray Ionization Mass Spectrometry

"Smart" polymers and polymer-protein conjugates find a vast array of biomedical applications. Ambient temperature reversible addition fragmentation chain transfer (RAFT) polymerizations conducted in an aqueous environment are a favorable method of choice for the synthesis of these materials; however, information regarding the initiation mechanisms behind these polymerizations-and thus the critical polymer end groups-is lacking. In the current study, high-resolution soft ionization mass spectrometry techniques were used to map the product species generated during ambient temperature gamma-radiation induced RAFT polymerizations of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) in aqueous media, allowing the generated end groups to be unambiguously established. It was found that trithiocarbonate and *R radicals produced from the radiolysis of the RAFT agent, *OH and *OOH radicals produced from the radiolysis of water, and *H radicals produced from the radiolysis of water, RAFT agent, or monomer were capable of initiating polymerizations and thus contribute toward the generated chain ends. Additionally, thiol terminated chains were formed via degradation of trithiocarbonate end groups. The current study is the first to provide comprehensive mapping of the formation pathways and end group patterns of stimuli-responsive polymers, thus allowing the design and implementation of these materials to proceed in a more tailored fashion.

Living Radical Polymerization by the RAFT Process—A First Update

This paper provides a first update to the review of living radical polymerization achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of Reversible Addition–Fragmentation chain Transfer (RAFT) published in June 2005. The time since that publication has witnessed an increased rate of publication on the topic with the appearance of well over 200 papers covering various aspects of RAFT polymerization ranging over reagent synthesis and properties, kinetics, and mechanism of polymerization, novel polymer syntheses, and diverse applications.