Functional group tolerance of AOTEMPO-mediated peroxide cure chemistry

- AOTEMPO-mediation of peroxide cures is examined for a range of polymers.
- Delayed onset is achieved with cure yield recovery for saturated polymers.
- Unsaturated polymers suffer from kinetic chain length issues and alkoxyamine instability.

Delayed onset formulations for the peroxide-initiated crosslinking of a range of commodity polymers are described. 4-Acryloyloxy-2,2,6,6,-tetramethylpiperidin-N-oxyl (AOTEMPO) is effective for controlling the crosslinking dynamics and yields of linear low density polyethylene (LLDPE), poly(ethylene-co-vinyl acetate) (EVA), poly(ethylene-co-propylene) (EPR), and poly(ethylene-co-propylene-co-ethylidenenorbornadiene) (EPDM). However, the cure additive is inefficient for butadiene-based materials such as 1,2-polybutadiene (vinyl-BR) and cis-1,4-poly(butadiene) (cis-BR), since macroradical trapping by AOTEMPO stunts diene-monomer oligomerization, thereby eliminating multiple crosslinks that cannot be restored by a single polymer-bound acrylate group. Additional crosslink yield losses arise from allylic alkoxyamine instability, the details of which are revealed by independent 1H NMR and rheology studies.

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