Gel point determination of gelatin hydrogels by dynamic light scattering and rheological measurements.

The sol-gel transition of gelatin aqueous solutions has been investigated in terms of time-resolved dynamic light scattering (DLS) and rheological measurements during the cooling process. A drastic increase in the scattering intensity, ergodic-nonergodic transition, and a power-law behavior in the scattering intensity-time correlation function were observed at the gelation temperature Tgel. Thus obtained "microscopic" Tgel was confirmed to be in good agreement with a "macroscopic" Tgel obtained by rheological measurements irrespective of gelatin concentration C . The fractal exponent Dp evaluated by DLS was found to be q and C independent and was also in good agreement with that obtained by rheology (n), i.e., Dp congruent with n congruent with 0.73, where q is the magnitude of the scattering vector.