There is an interest in organic catalysed reactions and recently, Hawker et al. reported an elegant metal-free ATRP process catalysed by an organic-based photoredox catalyst (PMMA, Ð = 1.18–1.32). Although sometimes heavy metals can be toxic, they are also essential for life (e.g. haemoglobin (Fe), vitamin B12 (Co)). Copper in particular is involved in many vital biological processes with a World Health Organization recommendation for a daily requirement of 0.6 mg per day12 with an estimated lethal dose in human adults of 10–20 g. It is noted that many organic molecules have much higher residual toxicity, including many monomers. In general, the use of transition metal catalysts for polymer synthesis is ubiquitous in our lives with catalyst residues safely left in products from, e.g. Ziegler–Natta polymerizations. Furthermore, ‘‘alternative ATRP techniques’’ have been developed which one could think might lower the complexity of the polymerization ((i) by ‘‘in situ’’ generating the active species). Recently, considerable interest has been directed towards controlling the activation–deactivation step
through external regulation,17 including photochemical stimuli. Copper-mediated polymerization in particular has shown potential with respect to photochemical control. The utility of light, as an external stimuli, actually eliminates the catalyst variable, although
all the aforementioned systems require an excess of ligand and careful optimization of the copper to ligand ratio in order to obtain the desired results. To the best of our knowledge, other attempts to address the complexity issues utilizing pre-formed copper complexes
have led to broadmolecular weight distributions,28 moderate conversions28 (B50–60%) at relatively high temperatures. Herein, a pre-formed, discrete Cu(II) formate complex was prepared and characterized prior to being utilized as a facile route to perform photo-induced polymerizations whilst maintaining excellent control over the molecular weight distributions at ambient temperature.