Strands vs crosslinks: degradation and regelation of poly(butyl acrylate) networks synthesized by RAFT polymerization Frances Dawson 1 , Touseef Kazmi 2 , Peter J. Roth 2 , Maciek Kopeć 1 1 University of Bath, UK, 2 University of Surrey, UK Covalently crosslinked polymer networks, such as thermoset materials are difficult to recycle and reprocess. To overcome this, degradable units can be incorporated into the network structure either within the crosslinker or into the polymer backbone, which can be cleaved chemically to produce soluble polymer fragments. Which method is more suitable depends on polymerization method, chosen monomer and whether repolymerization of the degraded fragments is targeted. While degradable crosslinkers containing a disulfide linkage may seem like a simple option, networks made by free radical polymerization (FRP) cannot be reliably degraded using this method. Instead, controlled radical polymerization techniques such as reversible addition–fragmentation chain transfer (RAFT) must be used to afford degradable poly(butyl acrylate) networks at a variety of crosslink densities. In comparison, dibenzo[c,e] oxepane-5-thione (DOT) can be used as a cleavable comonomer with n -butyl acrylate, allowing networks made by both FRP and RAFT to be fully degraded. [1] Both types of degradable networks can produce thiol-functional fragments, suitable for repolymerization through thiol oxidation to disulfides. However, structurally these fragments are very different, with fragments formed through disulfide cleavage in the crosslinker having a higher M n and lower dispersity than the fragments made through the C-S bond cleavage of copolymerized DOT. Both types of gels can successfully undergo 2 degradation/regelation cycles, with the DOT containing networks regelling most readily. References 1. H. Elliss, F. Dawson, Q. Nisa, N. M. Bingham, P. J. Roth, M. Kopeć, Macromolecules 2022, 55 , 6695–6702.
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