Mixing and Elastic Contributions to the Diffusion Coefficient of Polymer Networks

Because the swelling of polymer gels is a diffusion process of the polymer network, the swelling rate is determined by the diffusion coefficient of a polymer network. The diffusion coefficient (D) includes the polymer–solvent mixing contribution (Dmix) and the elastic contribution from the polymer network (Del). In this study, we experimentally investigate D, Dmix, and Del, using tetra gels whose network structural parameters are systematically controllable. We measured D and the shear modulus (G) using dynamic light scattering and dynamic viscoelastic measurement, respectively. According to the Tanaka–Fillmore theory, we evaluate Dmix and Del using the linear relationship between D and G in the as-prepared state. Consequently, we demonstrate a relation of D = Dmix + Del in the as-prepared, swelling, and equilibrium swollen states.