Characterization of crystallinity and mechanical properties of polyethylene functionalized with ester groups

Polyethylene (PE) is widely used material, yet only a small portion of it is currently recyclable. Functionalized PE, incorporating degradable ester groups in PE backbone to create PE mimics, can offer a way to enhance recyclability while maintaining mechanical properties. We develop a coarse-grained molecular dynamics model to study the effect of ester placement on crystallinity in HDPE and LDPE mimics by extending the united monomer model for PE (Fall et al., Macromolecules, 2022, 55, 8438), which accurately captures PE crystallization. We validate our model by comparing results with prior simulations and concurrent experimental studies. We show that an increase in ester fractions increases density, reduces crystallinity, and lowers melting and crystallization temperatures, consistent with prior studies and concurrent experiments. We quantify crystallinity using the local nematic order parameter, which measures local alignment of bond vectors. We find that ester beads are present in both amorphous and crystalline phases and observe a decrease in average stem length with higher ester fraction. Our work contributes to understanding of underlying mechanism of crystallization and melting in polyethylene functionalized with esters.