Material Design and Performance Study of Polyethylene Vitrimer: Effects of Crosslinking Density and Isomer Structure

This study reports the fabrication of a series of polyethylene‐based vitrimers (PE‐vitrimer) dynamically cross‐linked by isomeric phthalic acids (ortho‐, meta‐, and para‐, denoted as phthalic acid (PA), isophthalic acid, and terephthalic acid (PPA), respectively). The results indicate that ortho‐PA yields the most compact and homogeneous dynamic network owing to its favorable spatial accessibility of functional groups. Notably, an increase in crosslinking density did not restrict dynamic bond exchange; rather, it facilitated network mobility by decreasing the transesterification activation energy from 94.3 to 76.2 kJ·mol −1 , concurrently reducing the topology freezing temperature by ≈ 20 °C. This counterintuitive phenomenon is attributed to the increased concentration of dynamic β‐hydroxy ester bonds and the formation of a more homogeneous network, which effectively lower the exchange barrier. Consequently, the vitrimers exhibited simultaneous improvements in mechanical strength (tensile strength increased by 40.5% to 11.2 MPa) and reprocessability (over 90 % strength retention after two reprocessing cycles). These findings establish a molecular design framework coupling crosslinking density with isomeric configuration, offering a viable route for developing high‐strength, thermally stable, and recyclable PE‐vitrimer.