Oxygen‐mediated polymerization initiated by oltipraz‐derived thiones

Abstract

A pyrrolopyrazine-thione derived from oltipraz, a compound that has been investigated as a chemopreventive agent, affords radicals in the presence of thiols and oxygen via a redox cycle, an attribute that suggests its suitability as an initiator for oxygen-mediated polymerization. Here, we explore the utilization of this pyrrolopyrazine-thione, generated in situ from a precursor, as an initiator for the radical-mediated thiol–ene polymerization. While the pyrrolopyrazine-thione was shown to be capable of generating radicals in the presence of atmospheric oxygen and thiol groups, the reaction extents achievable were lower than desired owing to the presence of unwanted side reactions that would quench radical production and, subsequently, suppress polymerization. Moreover, we found that complex interactions between the pyrrolopyrazine-thione, its precursor, oxygen, and thiol groups determine whether or not the quenching reaction dominates over those favorable to polymerization.

Additive-Free Method for Enhancing the Volume Phase Transition Rate in Light-Responsive Hydrogels: A Study of Micro-Nano Bubble Water on PNIPAM-co-AAc Hydrogels

“…These findings imply that micro bubbles and nano bubbles contribute to increased gel stiffness. The mechanical properties of gels differ significantly between degassed and bubble water, affecting the kinetics and control of polymerization reactions [48,49]. While oxygen can serve as a free radical initiator [50,51], it may also quench radicals, inhibiting polymerization [52,53].…”

Evolution and Future Directions of Metal-Free Atom Transfer Radical Polymerization

“…Similarly, expansion to monomers with strongly absorbing functionalities and/or other photosensitive molecules needs to be addressed. Nevertheless, the sheer increase in monomer scope up to this point and key synthetic developments in areas such as improved oxygen tolerance , suggest that further expansion is just a matter of time. Not unlike its metal-based counterpart, fundamental and collaborative research in the area of metal-free ATRP will undeniably fuel future innovations that will lead to a plethora of previously inaccessible advanced materials in the same way classical ATRP has evolved over the past 20 years.…”