Composition–structure–property relationships of polyethylene vitrimers crosslinked by 8-arm polyhedral oligomeric silsesquioxane

Transforming polyolefins (POs), such as polyethylene (PE), into vitrimers is a promising research field due to their low cost, high availability, and excellent chemical resistance and mechanical properties. In these systems, the introduction of dynamic crosslinking can affect the degree of crystallinity in POs and may lead to phase separation due to incompatibility between the PO matrix and crosslinking agents, both of which can impact mechanical performance. This study investigates the relationship between crystallinity, crosslinking, and thermal-mechanical properties in commodity PE-derived vitrimers utilizing reactive 8-arm polyhedral oligomeric silsesquioxane (POSS) nanoparticles by deconvoluting the crosslinked and non-crosslinked components. Specifically, the insoluble crosslinked components displayed a lower modulus and increased brittleness, while the non-crosslinked phase performed similarly to neat PE. Together, the PE-vitrimer, crosslinked with 8-arm POSS, exhibited reduced toughness, elongation at break, and a slight increase in ultimate tensile strength. These behaviors were consistent when comparing the crosslinking density and gel fraction with a bifunctional crosslinker analogue. This work demonstrates the influence of multi-arm, nanoparticle-based crosslinker content on the mechanical properties of semi-crystalline PO-vitrimers, elucidating the roles of network density and crystallinity in determining their performance.