Immiscible polymer blend compatibilization through pendant ionic interactions

Polymer recycling is critical for reducing plastic waste, but various challenges result in less than 10% of plastics actually being recycled. One issue that limits mechanical recycling is the immiscibility between dissimilar polymers that results in macrophase separation and poor material properties for the resulting blend, necessitating sorting of different polymeric materials. Prior theoretical work has suggested that small numbers of ionic interactions can be used for immiscible polymer blend compatibilization. Here, we demonstrate that low levels of incorporation of ionic bonds (as low as 0.5 mol%) formed via sulfonic acid to imidazole base proton transfer mechanism results in the formation of optically clear and phase mixed blends in an otherwise incompatible poly(styrene) and pol(butadiene) mixture. The model system is then extended to industrially-relevant, semi-crystalline poly(ethylethylene) ionomers via hydrogenation of the functionalized poly(butadiene). Processing studies, mechanical testing, and small angle X-ray scattering reveal the macroscopic and microstructural behavior of the blends at various ionic functionalization levels and polymer molecular weights, highlighting the underlying rich physics of immiscible polymer blends with sparse incorporation of charged groups. This work is opening numerous avenues in exploiting ionic interactions as a strategy for addressing the current plastic waste challenge.