One of the major barriers for degradation/depolymerization of commodity plastics is the chemical and thermal resistance of the strong C-C bonds in polymer backbones. Introduction of dynamic covalent bonds such as siloxane linkages would allow for the cleavage of the polymer backbone with possible avenues for reprocessing/recycling. In our study, siloxane linkages were introduced at a specific location in the polymer backbone which allows for scission and exchange of the polymer strands using a catalyst, fluoride source is commonly used. Performing atom transfer radical polymerization (ATRP) using initiators containing siloxane linkages on styrene or methyl methacrylate as model systems, we synthesized polymers with cleavable and exchangeable linkers. Exchange of siloxane linkage between the above-mentioned polymers and 1,3-divinyl tetramethyldisiloxane (DVTMS) using Tetra-n-butylammonium Fluoride (TBAF) as the catalyst was performed. Characterization by gel permeation chromatography (GPC) shows reduction of molecular weight by a factor of two, consistent with cleavage at the mid-point. NMR spectroscopy (<sup>1</sup>H, <sup>13</sup>C) demonstrates the incorporation of a vinyl end-group from exchange with DVTMS. Further elaboration of the reactive end-group is possible by using known vinyl chemistries. The findings from the cleavage experiments reveal the potential of utilizing dynamic covalent bonds in the field of chemical upcycling of plastics. Incorporation of siloxane linkages can be a strategy for developing a much-needed closed loop of chemical/polymer circularity.

Synthesis of cleavable polymers by the introduction of dynamic covalent bonds within the backbone

ACS Spring Meeting 2021

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