(167v) Consecutive Photoinduced Electron Transfers for Visible-Light Photocatalytic Polymer Synthesis

The importance of photoinduced electron transfer (PET) reactions was recognized since the early days of photopolymerization as a field. Inspired by the photographical sciences, several pioneers, such as D.F. Eaton, identified the potential of visible-light induced polymerizations using organic dyes. The energetic limit of photolysis was evident and thus it was clear that the field needed a conceptual framework for the prediction of the kinetics of photoinitiation with the later called “multi-component” systems. That was the birth of the connection between Rehm-Weller and Marcus kinetics with polymer chemistry. Later, J. Packowski dedicated substantial efforts to the incorporation of Marcus theory into polymerization schemes. However, the incorporation of PET kinetics and thermodynamics remains challenging and limited. The latter generally goes unrecognized, even now that numerous researchers report PET schemes for modern applications of polymerization reactions, such as in Additive Manufacturing. Furthermore, advances in the elaboration of classical PET schemes have remain elusive. Here, we describe our discovery of the use of Consecutive Photoinduced Electron Transfers (Con-PET) in the context of polymer synthesis and contemporary to the development of the general Con-PET concept by Burkhard König. We then summarize the latest developments in Con-PET from a synthetic organic chemist approach to illustrate promising connections to the polymer chemistry arena. We attempt to provide a general outlook of this strategy by analyzing the kinetic and thermodynamic considerations as a function of molecular structure and reaction environment. This allows us to introduce our latest advances in a comprehensive kinetic model of such complex reaction networks, which has recently enabled us to propose a new type of photoredox catalysis scheme for the synthesis of polymers activated by free radicals. We hope that this talk provides a historical perspective that culminates in the visualization of the new avenues for the implementation of multi-molecular photoinitiating systems in polymer chemistry.