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

Small-angle neutron scattering measurements are reported for experiments pe rformed on mixtures of gelatin and glutaraldehyde (GA) in the aqueous phase , where the gelatin concentration was fixed at 5% (w/v) and the GA concentr ation was varied from 1.25 x 10(-4) to 3 x 10-3%(w/v). Two length scales as sociated with this system were identified in both sol (60 degrees C) and ge l state (28 degrees C). One of these, the correlation length (xi) or mesh s ize of the cross-linked network showed negligible dependence on temperature , but a scaling xi similar to [GA](r), where [GA] is the concentration of c ross-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 tr ansformed from a sol to gel state for all [GA]. Observations are discussed in the context of the results obtained from dynamic light scattering experi ments performed earlier.