Inhomogeneities in poly(acryrlamide) gels: position-dependent elastic modulus measurements

The inhomogeneities in poly(acrylamide) (PAAm) gels and the formation mecha nism of inhomogeneities were investigated using the results obtained by the mechanical measurements. The gels in the form of rods of 5.6 mm in diamete r were prepared at various crosslinker (N,N'-methylene(bis)acrylamide) cont ent. The initial monomer concentration was set to 5.1 w/v %. The results sh ow that the elastic modulus of PAAm gels varies depending on the location, at which the mechanical measurements are carried out. The modulus increases with increasing distance from the bottom of the gel rod. The extent of mod ulus variation along the gel increases with increasing crosslinker content from 2.6 to 9 % BAAm.