Depolymerization protocol for linear, branched, and crosslinked end-of-life silicones with boron trifluoride diethyl etherate as the depolymerization reagent

Abstract

An important issue for current society is the accumulation of large amounts of end-of-life polymers, which are mainly deposited in landfills, converted by thermal recycling or down cycling to low-quality materials. In contrast to that, the feedstock recycling of end-of-life polymers to produce new high-quality polymers is only applied to a small portion of waste. In more detail, low-molecular weight chemicals are generated by this methodology; they can be polymerized in a second step to produce new high-quality polymers. Notably, with these depolymerization-polymerization processes, contributions to a more sustainable, resource-conserving, and environmentally benign society can be made. In this regard, we have set up a capable protocol for the depolymerization of polysiloxanes, which are applied extensively in numerous technological applications. Boron trifluoride diethyl etherate was used as a depolymerization reagent to transform Si-O bonds in linear, branched, and crosslinked silicones to Si-F bonds. As depolymerization products, difluorodimethyl silane for linear polysiloxanes and methyl trifluorosilane for branched polysiloxanes were obtained; these were suitable synthons for new polymers and will allow an overall recycling of polysiloxanes.