1 research outputs found
Impact of Organometallic Intermediates on Copper-Catalyzed Atom Transfer Radical Polymerization
In
atom transfer radical polymerization (ATRP), radicals (R<sup>•</sup>) can react with Cu<sup>I</sup>/L catalysts forming
organometallic complexes, R–Cu<sup>II</sup>/L (L = N-based
ligand). R–Cu<sup>II</sup>/L favors additional catalyzed radical
termination (CRT) pathways, which should be understood and harnessed
to tune the polymerization outcome. Therefore, the preparation of
precise polymer architectures by ATRP depends on the stability and
on the role of R–Cu<sup>II</sup>/L intermediates. Herein, spectroscopic
and electrochemical techniques were used to quantify the thermodynamic
and kinetic parameters of the interactions between radicals and Cu
catalysts. The effects of radical structure, catalyst structure and
solvent nature were investigated. The stability of R–Cu<sup>II</sup>/L depends on the radical-stabilizing group in the following
order: cyano > ester > phenyl. Primary radicals form the most
stable
R–Cu<sup>II</sup>/L species. Overall, the stability of R–Cu<sup>II</sup>/L does not significantly depend on the electronic properties
of the ligand, contrary to the ATRP activity. Under typical ATRP conditions,
the R–Cu<sup>II</sup>/L build-up and the CRT contribution may
be suppressed by using more ATRP-active catalysts or solvents that
promote a higher ATRP activity