Structural analysis of ethylene ionomers containing two types of metal ions*

Polymers with a small amount of ionic groups introduced into a hydrophobic polymer are called as ionomers. In particular, ethylene-based ionomers with polyethylene as the main chain have high toughness and transparency. These polymers are used for packaging films and sporting goods.

These features are thought to be due to the formation of aggregation structures by hydrophilic ionic groups, called as ionic aggregates. The purpose of this study is to clarify the effect of ionic aggregates containing various metal ions.

From the results of DSC, we observed the so-called Ti peak due to melting small crystallites around ion aggregates. The Ti peak temperature increased with blending the two different metal ions, because of increase in the small crystallite’s size. In-situ temperature-controlled X-ray scattering measurements were performed focusing on the ion aggregates during the melting of the small crystallites and lamellar crystals. The results showed that the ion aggregates expanded after melting small crystallites. It was considered that the ion aggregates and the crystal were inhibiting each other at room temperature, and that the ion aggregates expanded with the melting of the crystal.