Friday, March 23, 2012 - 12:00pm
Membranes for Clean Water Project, Polymers Division, NIST
Many membrane technologies including water purification, fuel cell and drug delivery make advantageous use of thin swollen polymer network layers to facilitate permselectivity. Thus, understanding the critical time- and length-scales that regulate their transport behavior is critical to developing membrane materials with enhanced performance. In this talk, a recently developed indentation-based measurement technique is presented that couples contact mechanics to mass transport in order to quantify solution diffusion within hydrogels. Termed Poroelastic Relaxation Indentation (PRI), the technique measures the poroelastic relaxation time required for solvent molecules or solvated polymers to migrate away from the deformed region of the polymer network due to an applied deformation imposed by an indenter. We demonstrate this technique for model thin hydrogel layers and show that by linking the poroelastic relaxation time to well-established contact mechanics theory, several materials properties including diffusion coefficients, shear modulus and average pore dimensions of the hydrogel can be determined in a straightforward manner.