C–H chlorination and bulk depolymerization of commercial poly(methyl methacrylate)

Abstract

Accumulation of waste poly(methyl methacrylate) (PMMA) plastics is posing threats to the environment. Thus, it is highly desirable to develop good and versatile processes to recycle waste PMMA since only about 10% of it can be recycled now. While depolymerization triggered by halogen chain ends of PMMA in solution is well established, few examples can accomplish efficient bulk depolymerization of commercial PMMA. In this work, we developed a stepwise strategy, that is facile and mild C–H chlorination methods to install Cl groups into the PMMA backbone as side chain triggers to initiate efficient bulk depolymerization. In bulk depolymerization, the synthesized PMMA, commercial PMMA with different M_n values (10⁴ to 10⁶ g mol⁻¹) and PMMA-based acrylic sheets are all suitable for recovering the pure MMA monomer effectively with high yields (up to 81%) at 290 °C, which is significantly lower than the pyrolysis temperature in industry. Additionally, our method not only tolerates various additives commonly used in industry, but is also suitable for the depolymerization of gram-scale acrylic sheets. This strategy can potentially shed light on the advancement of bulk depolymerization of other vinyl polymers.