Dynamic mechanical response of solid polyelectrolyte complexes at varying temperature, humidity and pH

The dynamic behavior of polyelectrolyte complexes (PECs) is of interest for applications ranging from health to personal care. Hydration is an important factor, but its effect on the dynamic of PECs is poorly described. Previously in our group, time-temperature (TTSP) and time-water superposition (TWSP) principles were applied to show equivalency between temperature and water for poly(acrylic acid) (PAA) – poly(allylamine hydrochloride) (PAH) PECs. However, information is lacking regarding the relaxation time of intrinsic ion pair in these PECs at different pH values and the role played by water. Here, we describe the dynamic mechanical behavior of PAA-PAH solid PECs at different pH values, hydration and temperature. The temperature shift factor followed an Arrhenius relation and the water shift factor, obtained after TWSP enabled the study of the relaxation time of intrinsic ion pairs at different water content. Differential scanning calorimetry experiments were performed to quantify the amount of “bound water” and show that bound water provides a major contribution to relaxation.