摘要：When a polymer gel absorbs solvent from surrounding, stress field is created in the gel, and this causes complex dynamics of the swelling behavior. For example, a thin gel sheet bends as liquid penetrates from one side of the surface. We develop a diffusio-mechanical theory for gel dynamics. We calculate the time dependence of the bending behaviors for two types of gels. (a) a free gel that can swell in all directions freely, and (b) a bound gel the bottom surface of which is adhered to a plastic film which can bend but cannot stretch. The theory shows that the bending behaviors of the two gels are distinctively different. The free gel bends as the liquid penetrates, and takes a maximum curvature, and then slowly bends back to take the original flat shape. On the other hand, the bound gel keeps bending, and gets an equilibrium state in a bent configuration. For gel swelling, we show that (a) while the macroscopic thickness and the radius of the gel increases monotonically in time, the gel is compressed near the mid-plane, and that (b) while the swelling time depends on the shear modulus $G$ of the gel, its dependence is weak, and the time is mainly determined by the friction constant of the gel network and the osmotic bulk modulus of the gel. We also show that these characteristic features are reproduced accurately by a simple variational calculation for the gel deformation. An analytical expression is given for the gel dynamic time.