Enhancing the Glass Transition Temperature of PMMA Particles via Internal Polymer–Salt Hybrid Interfaces

Poly(methyl methacrylate) (PMMA) particles are widely used due to their excellent dispersibility, surface tunability, and suitability for forming monodisperse polymer particles. However, the relatively low glass transition temperature of PMMA (typically around 114 °C) restricts its thermal applicability. In this work, we developed a one-step dispersion polymerization to prepare PMMA–salt-cluster hybrid particles and systematically examined the influence of Li salt concentration, counteranion, solvent composition, and monomer concentration. In methanol/water, monodisperse particles ( C v < 5%) were obtained with modest T g increases (121.6 °C), indicating limited Li + incorporation. Polymerization in nonpolar cyclohexane further increased Li uptake and T g up to 131.9 °C. Molecular dynamics simulations suggest that salt aggregation creates internal polymer–salt interfaces that can function as physical cross-linking domains, providing thermal reinforcement at the particle level.