Effect of Cations on Glass Transition Temperature and Fragility of Polyelectrolyte Complexes

Glass transition temperature (Tg) in polyelectrolyte complexes (PECs) is essential for understanding these material's thermal and mechanical behavior, impacting their application in fields like drug delivery and energy storage. Doping ions in the PEC have been shown to plasticize its matrix. While literature offers interesting insights into the thermodynamic impacts of these ions, very little is known about their impact on the PEC's Tg and fragility, which quantifies the deviation of relaxation dynamics from Arrhenius behavior. Recent work, including studies along the Hofmeister series, has highlighted the influence of monovalent anion type in reducing the PEC's Tg. However, Tg and fragility remain largely unexplored concerning cation type. In a previous study from our group, we discussed how Tg (measured using DSC and Broadband Dielectric Spectroscopy) and fragility vary with cohesive energy density in PECs, and compared their trends with the Generalized Entropy Theory (GET). This talk builds on these findings, probing how monovalent and divalent cations may affect Tg, cohesive interactions, and ultimately, PEC fragility. Understanding the cation-specific effects on Tg and fragility provides a more comprehensive insight into how ionic species jointly impact the thermal nature of PECs, which is vital in designing PEC-based materials for scores of applications.