Nanoscale Morphology in Disodium Salt-Anchored Polyethylene Ionomers

Abstract

A molecular-level understanding of the ion cluster morphology is crucial to designing the structure and enhancing the properties of random polyethylene ionomer. Here, we report that the strategic addition of aliphatic disodium salt has a pronounced effect on the mechanical properties and nanoscale morphology. With the addition of various aliphatic disodium salts, both the tensile strength and Young’s modulus are significantly increased. By comparing the results of atomistic molecular dynamics simulations with experimental characterization data, the ionic cluster nanoscale morphology varies with different chain-length disodium salts, while maintaining the crystallization of the polyethylene matrix. The alkyl disodium salts with relatively short alkyl chains (<C8) tend to anchor to the same cluster, forming encapsulation or loop structure. The alkyl disodium salts with relatively long alkyl chains (>C12) bridge between clusters by anchoring to two different clusters, helping to redistribute the clusters within the polymer matrix and providing additional cross-link strength. The cluster morphological evolution during stretching was simulated, and its relation to mechanical properties is comprehensively discussed. This, in turn, unlocks the potential for structural regulation at the nanoscale by additive manufacturing to enhance the performance.