Impact of Charge Placement on Polymer Blend Compatibilization

Tailoring the properties of polymer blends requires the ability to control polymer phase behavior. While ionic interactions effectively compatibilize immiscible polymer blends, predicting or tuning the blend microstructure remains elusive. Here, we integrate theory and experiments to demonstrate the effect of charge placement on blend compatibilization and resulting microphase behavior. Model poly(methyl acrylate) and poly(styrene) were functionalized with tertiary amine and sulfonic acid groups either randomly or as blocks, at a constant 5 mol% functionality and volumetric degree of polymerization. Upon stoichiometric blending, ionic bonds generated via acid-base proton transfers yielded optically clear materials that were characterized by small-angle X-ray scattering. Experiments were consistent with theoretical predictions, where blends with a blocky component exhibited ordered microstructures while the purely random blend was disordered, demonstrating a direct correlation between the charge placement and microstructure. The link between microphase and macroscopic behavior was shown through blend viscoelasticity measured by oscillatory rheology. These insights provide a framework for designing tailored polymer blends, offering relevance to the challenge of mixed plastic waste recycling.