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, lowmolecular weight chemicals are generated by this methodology; they can be polymerized in a second step to produce new highquality polymers. Notably, with these depolymerization-polymerization processes, contributions to a more sustainable, resourceconserving, 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 SiAO bonds in linear, branched, and crosslinked silicones to SiAF 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.

The current waste management system is based primarily on landfills, thermal recycling and down-cycling. On the other hand, only a small portion of the end-of-life materials is recycled by depolymerization. In more detail, low-molecular weight commodities/monomers are produced by this process, which can be polymerized in a second step to produce new high quality polymers. Importantly, by applying these depolymerization/polymerization methodologies, contributions to more a sustainable, resource-conserving and environmental-benign society can be made. In this regard, we have set up a capable low-temperature (100°C) protocol for the depolymerization of poly(dimethylsiloxane)s. In more detail, boron trifluoride diethyl etherate was applied as a depolymerization reagent in the conversion of numerous silicones to obtain difluorodimethylsilane and 1,3-difluoro-1,1,3,3-tetramethyldisiloxane as well-defined products under solvent-free conditions in yields up to 85%. Moreover, it was demonstrated that difluorodimethylsilane and 1,3-difluoro-1,1,3,3-tetramethyldisiloxane are useful starting materials for the synthesis of new silicones (polymerization). In consequence a recycling of silicones is feasible. The principle of operation of the recycling concept was demonstrated in the depolymerization/polymerization of 500 g of a polysiloxane.

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