Investigation into the ageing process in gels of gelatin/water systems by the measurement of their dynamic moduli

Brillouin light scattering from a biopolymer gel: hypersonic sound waves in gelatin

“…Like Ng and coworkers [19,20], we find that the network velocity of sound is proportional to 4b ~/2, and that the agreement between theory and experiment is very good. Remarkably, the explicit concentration dependence assumed above for the network (longitudinal) high-frequency sound velocity is in agreement with the observed concentration dependence of the low-frequency shear modulus of gelatin, G', which is proportional to the square of the gelatin concentration [21]: the low-frequency (shear) velocity of sound must be proportional to ~1/2 then, since it is proportional to (G'/pn) 1/2 and since the network density is proportional to ~b. (It is interesting to note that from scaling theory it is found that for swollen gels that G oc ~b 2'25 for a given solvent and fixed functionality [22].…”

“…(It is interesting to note that from scaling theory it is found that for swollen gels that G oc ~b 2'25 for a given solvent and fixed functionality [22]. The power 2.25 is slightly higher than the value 2 usually attributed to gelatin [21]. As a consequence, the resulting power for the concentration dependence of the network sound velocity would be somewhat higher than 0.5)…”

On the nature of crosslinks in thermoreversible gels

“…Apparently, temperature determines the lowest sequence length that is stable: at lower temperatures smaller sequence lengths are stable, so that more crosslinks are present. In this aspect results for solutions with different temperature histories are very interesting [44]: a solution that was preheated at 120 ºC shows a much higher tendency to form gels than a solution that was, as usual, preheated at 145 ºC. This appeared from a hundredfold faster increase of the storage modulus at 120 ºC.…”

“…above 2 %, with triple helical crosslinks, hence with a functionality equal to 6. The network formation is very fast: for a 2% aqueous gelatin (M w =70 kg/mol) a rubber plateau is already present after 6 min [4,7,44]. The plateau modulus increases fast in the course of time and the network seems quite permanent.…”

Study of structure and dynamics of gelatin gels by temperature ramped holographic relaxation spectroscopy

“…In TR-HRS, Tm can be measured from the intensity relaxation profile without introducing any kind of mechanical or chemical perturbation of the gel. Based on the observed gel content versus the setting time, it is found that the gelation process is first order, apparently in disagreement with other investigations (Ref.6,(23)(24)(25)(26). In addition, the mobility of the small fluorescein molecule in the gels was also investigated by HRS.…”