Small-angle neutron scattering studies of chemically cross-linked gelatin solutions and gels

Small-angle neutron scattering measurements are reported for experiments performed on mixtures of gelatin and glutaraldehyde (GA) in the aqueous phase, where the gelatin concentration was fixed at 5% (w/v) and the GA concentration was varied from 1.25 x 10(-4) to 3 x 10-3%(w/v). Two length scales associated with this system were identified in both sol (60 degrees C) and gel state (28 degrees C). One of these, the correlation length (xi) or mesh size of the cross-linked network showed negligible dependence on temperature, but a scaling xi similar to [GA](r), where [GA] is the concentration of cross-linker GA, was observed with v = 0.33 +/- 0.04 in the gel state. Other length scale associated was the size of inhomogeneities zeta which showed no [GA] dependence but showed appreciable increase in size as the system transformed from a sol to gel state for all [GA]. Observations are discussed in the context of the results obtained from dynamic light scattering experiments performed earlier.