Optimizing light exposure in photochemical polymer recycling for sustainable 3D printing

Remarkable growth of the 3D printing industry in recent decades has also caused a rapid growth in waste production, as over 30% of 3D-printed material is discarded immediately after printing. To enable recycling and reprocessing of scrap printing materials, we report photo-responsive polymer networks that are crosslinked, un-crosslinked, and re-crosslinked in response to light, demonstrating the potential of photochemical recycling as a low-cost, low-energy, on-demand technology. We designed photo-recyclable polymer networks comprising multi-arm star polyethylene glycol functionalized with anthracene (PEG-anthracene). PEG-anthracene undergoes network formation upon irradiation with ultraviolet light (UVA, 365 nm) and network deconstruction upon irradiation with short-wavelength ultraviolet light (UVC, 265 nm). Recyclability is optimized by reducing anthracene crosslink density and maximizing un-crosslinking by tuning polymer architecture, concentration, and light exposure profiles. These findings demonstrate an opportunity for on-demand recycling of photo-responsive polymers to improve the sustainability of 3D printing.