Researchers have developed a chemical recycling method for silicone polymers that breaks them down into their basic building blocks. The process uses deoxygenative chlorination, involving phosgene or its substitutes, to cleave the silicon-oxygen bonds in siloxane materials under mild conditions. This regenerates dichlorosilane monomers, which are industrially valuable feedstocks.
The work addresses a long-standing challenge in silicone recycling. Silicones' thermal stability and chemical inertness, which make them useful in industrial, medical, and consumer applications, also make them difficult to recycle chemically. Current waste management relies primarily on landfill storage, incineration, and mechanical recycling.
The research team found that phosgene acts not just as a chloride source but forms a chlorocarbonyl cation when activated by a silylium ion. This reactive intermediate serves as the active agent that breaks Si-O-Si linkages. Mechanistic investigations and computational calculations support this mechanism.
The method works on a broad range of siloxane materials, including linear and cyclic forms, commercial silicone oils, and elastomers. The researchers describe this as a feedstock recycling process applicable to the sustainable circular recycling of siloxane materials.
The research appears in Nature as an early-access, peer-reviewed, accepted article.