Hydration and ion interactions of zwitterionic homopolymers with varying carbon spacer lengths

We use molecular dynamics simulations to examine the role of polymerization and changing monomer carbon spacer length on the hydration and ion association properties of carboxybetaine and sulfobetaine zwitterionic homopolymers with LiCl and KCl salts in aqueous solution. Our simulation results suggest that polymerization leads to increased water and ion effective residence time compared to previous studies while varying carbon spacer length causes a change in the partial charge of zwitterionic functional groups. This change in partial charge affects the distribution and quality of water and ion interactions. Additionally, investigating the ionic conductivity by use of the Nernst-Einstein equation, we found that KCl had higher conductivity than LiCl for both polymer types, which is explained by the shorter effective residence time of K+ ions to the polymer than that of Li+.