Spatially-resolved Dynamics of Poly Vinyl Alcohol Gels.

Hydrogels are cross-linked polymers held together in a network by covalent bonds and swollen in water. The large volume fraction of solvent gives these materials unique physical properties, which makes them ideal for applications like absorbents, drug delivery, and tissue engineering. Studying the dynamics of the hydrogels is necessary to understand and engineer hydrogels with respect to each application. While much research effort has focused on understanding gel dynamics in the bulk, very little is understood about the effect of directional stresses, and how the networks respond locally. Here, we stretch poly(vinyl alcohol) gels and study the resulting dynamics parallel and perpendicular to the direction of deformation using dynamic small angle light scattering. We find that the rate of elastic motion increases in the direction of stretching and decreases in the perpendicular direction. This study will help understand how gels perform locally under stress.