THE TRANSITION ZONE FOR GELATIN GELS AS MEASURED BY HIGH-FREQUENCY RHEOLOGY

The high-frequency (100 Hz-200 kHz) linear viscoelastic behaviour of g elatin in the transition zone was investigated. During the early stage s of ageing, the dynamic shear modulus for a 4 wt% gelatin gel at the gel point at 25 degrees C was found to vary according to a power law G ' proportional to G '' proportional to omega(n), with n approximate to 0.75. Within the framework of a recent model by Groot et al. [J. Chem . Phys., 104, 9202 (1996)], this value is consistent with a result der ived earlier from large deformation rheology, suggesting that the netw ork bonds in a gelatin gel are more stretched than an ideally swollen polymer chain. However, ageing effects observed in large deformation e xperiments are not observed for the small deformation high-frequency d ata.