Behind the scenes of green chemistry: Glories and shadows of atom transfer radical polymerization environmental impact (E-factor)

The paper presents the evaluation of environmental impact (E-factor) as green chemistry metric, calculated for polymer synthesis via one of the most useful tools of macromolecular chemistry, which is atom transfer radical polymerization (ATRP), belonging to the reversible deactivation radical polymerization (RDRP) techniques. For the first time, experimentally determined polymerization yields were included in the calculation, by analyzing the polymer synthesis process using various organic solvents, different methods of regenerating the catalytic complex (meaning ATRP approach), or using the miniemulsion system as eco-friendly reaction medium and presenting the possibility of effective solvent recovery and reuse. The majority of the values of E-factor were below 16, falling within the scope intended for fine chemicals (5–50). The significant and innovative part of the presented research involves verifying the feasibility of using higher concentrations of the dispersed phase in the case of miniemulsion polymerization (increased to as much as 100 % vs. aqueous phase from a typical 20 %), while the use of recycled water allowed a 3-fold reduction in E-factor value. Polymerization in a miniemulsion environment is also attractive due to its low cost, considering the price of distilled water, which is over 580-fold lower than that of DMSO – a typical organic solvent. These observations allow for the reduction of environmental impact and process cost. Importantly, the observed trends in E-factor changes allowed for the identification of ATRP development directions in line with green chemistry and the circular economy.