Glass transition confinement dynamics of polyzwitterions in the presence of charged ions

The confinement dynamics with respect to the glass transition observed in polyzwitterions (PZIs) have been shown to be analogous to the confinement dynamics of semi-crystalline polymers [1]. PZIs contain a covalently linked anion and cation allowing them to form dipolar crosslinks. When dissolved in salt solutions the charged ions associate onto these zwitterionic moieties blocking the formation of the dipolar crosslinks. PZIs based on sulfobetaine were synthesized: poly(sulfobetaine methacrylate), poly(sulfobetaine acrylate), and poly(ethyl sulfobetaine methacrylate). Each PZI was blended with LiCl, Na₂SO₄, NH₄Cl, and Choline Chloride at various molar ratios of monomeric units to ionic units. Using differential scanning calorimetry and fast scanning calorimetry, direct measurements of confinement can be made through the analysis of the glass transition relaxation process. Comparing highly confined and fully unconfined materials, the one with greater confinement will have a high glass transition temperature (T_g) and a smaller change in heat capacity at T_g. Through chemical changes and salt addition, we show that the disruption of crosslinking through ion association decreases the confinement, creating a more mobile structure. This increased mobility and capacity to store molar ratios of salts makes these materials candidates for use as drug carries in pharmaceuticals, solid polymer electrolytes, filtration membranes, and biomedical applications.





1. Thomas, J., Chum, S., Deucher, W., Mondal, A., Asatekin, A. and Cebe, P., Thermal and structural properties of polyzwitterions: Effects of monomer chemistry and salt addition. Thermochimica Acta, 2023. 730: p. 179617.