Dynamic Crosslinking of Polyethylene by Hydrogen Bonding Grafted Motifs: A Molecular Dynamics Simulation Study

The recyclability of polyethylene-based is an important social and environmental issue. Dynamic crosslinking of polyethylene by multiple hydrogen bonding motifs provides an opportunity for complete recyclability. This approach is based on producing reversible covalent bonds in the crosslinking polyethylene networks to produce vitrimers. It is employed molecular dynamics simulation to study the effect of mole percent of randomly grafted 1-(7-oxo-7,8-dihydro-1,8-naphthyridin-2-yl) poly(ethylene-co-[2-hydroxyethyl methacrylate])s (ODIN-PEHEMAs), on thermal stability of the vitrimers. The crosslinking nature and dynamics of these grafted polyethylene chains are analyzed focusing on free volume, specific volume, radial distribution function, and mean squared displacement. The addition of hydrogen bonding units increased the free volumes, but the mole percent of side chains is not enough to affect the dynamics of the main chains in vicinity of the glass transition temperature. The simulation results show that for 1.67-mole percent of randomly grafted ODIN-PEHEMAs, the mean squared displacement, MSD, dramatically increases in vicinity of 312.5 K, which is in good agreement with the experimental results due to the physical cross-linking breakage at room temperature. With increasing the mole percent of ODIN (4.33, 8.33, and 10.67 mole percent), the breakage of physical cross-links shifted to higher temperatures.