Bulk depolymerization of PMMA using difunctional pyromellitic or monofunctional phthalimidic ATRP initiators

• ATRP allows the synthesis of polymers with retained chain end functionality needed for depolymerization at lower temperatures. • Pyromellitic or phthalimidic moieties provide additional depolymerization functionalities. • Bulk depolymerization provides enhanced sustainability. • Network depolymerization was possible because of the use of degradable pyromellitic diimide crosslinker, which triggered the depolymerization in bulk above 220 °C. This study presents a new approach for enhancing the depolymerization efficiency of poly(methyl methacrylate) (PMMA) by incorporating multiple depolymerization sites within the polymer chains. Four distinct PMMA polymers were synthesized, each bearing different combinations of phthalimide ester and chloride, or bromide functionalities placed in specific positions in the polymer chain. The polymers were prepared by atom transfer radical polymerization. Increasing the number of activation sites enhanced the depolymerization yield. Experiments conducted under reduced pressure in bulk revealed depolymerization yields ranging from 73 % to 86 % achieved within 30 min at 220 °C. Thermogravimetric analysis performed on polymers with four different molecular weights demonstrated the efficiency of this approach also for polymers with higher molecular weights. A similar strategy was also performed on crosslinked networks by incorporating activatable pyromellitic moieties to reach 85 % of depolymerization yield. This strategy demonstrates the potential for efficient depolymerization of PMMA at relatively low catalyst loadings and temperatures, offering promising prospects for sustainable polymer recycling processes.