Photocatalytic ATRP Depolymerization: Temporal Control at Low ppm of Catalyst Concentration

Our group investigated the photocatalytic depolymerization of ATRP-synthesized polymers under mild conditions using environmentally friendly, non-toxic iron based catalyst. Depolymerization of polymers synthesized by controlled radical polymerization enables the regeneration of virgin-quality raw materials which can be subsequently subjected to an unlimited number of re-polymerization/recycling cycles. Present chemical recycling strategies typically operate under extreme dilute conditions, require high temperatures and catalyst loadings, and do not allow for temporal regulation over the depolymerization. In the current study, we propose a photocatalytic ATRP depolymerization which significantly suppresses the reaction temperature from 170 to 100 °C while enabling temporal regulation. Specifically, in the presence of low ppm catalyst concentrations, the depolymerization during the dark periods could be completely eliminated, thus allowing to modulate the rate by simply turning the light “on” and “off”. Notably, our approach could be carried out at high polymer loadings (up to 2M), and by preserving the end-group fidelity near-quantitative depolymerization conversions (up to 90%) could be reached. This methodology provides a facile, environmentally friendly and temporally regulated route to chemically recycle ATRP-synthesized polymers, thus opening the door for further opportunities both in the fields of chemical recycling and reversed lithography.