Proton diffusion in PAM hydrogels

Abstract Hydrogels are widely used in the field of biomedicine because of their excellent biocompatibility. In most cases, the pH range applicable to drugs is limited, so it is meaningful to study the diffusion of protons in hydrogels. In this work, the diffusion rate of protons in hydrogels was monitored by a self‐made device, and the factors affecting the diffusion rate of protons were studied. The self‐made device consists of a supply chamber and a receiving chamber with a piece of hydrogel sandwiching between them. It was found that the thickness of hydrogel had a great influence on proton diffusion. The thicker the hydrogel is, the slower the proton diffusion rate is. At the same time, the diffusion coefficient of protons in PAM hydrogel was calculated to be 1.28 ± 0.09 × 10 −5 cm 2 /s (HCl, 25°C). The diffusion coefficient is a function of temperature, and its value increases with the increase in temperature. The effect of the solid content of hydrogel on proton diffusion was also considered, but in the range of solid content 1.81%–10.07%, the proton diffusion rate was almost unaffected. Moreover, anions also have a decisive effect on proton diffusion, with smaller anions leading to faster proton diffusion in the hydrogel.