PMDETA instead of BiPy as a ligand was also tried, but this only yielded thin brushes (no thicker than 50 nm after 4 h) and uncontrolled polymerization (nonlinear thickness over time). It is not completely clear why the polymerization is so poorly controlled with PMDETA, but it is mentioned in literature that the Cu(II)/PMDETA complex is unstable towards protonation, which could be problematic in ARGET as protons are released as a side product of the oxidation of the reducing agent .