Is it mandatory that in the case of determination of sol-gel transition of a hydrogel G' and G'' cross? In my case I am running isothermal scans to determine the sol-gel transition, but G'and G'' never has a crossover. (They do increase at a particular temperature), I have varied the strain value as well as the frequency but still its the same. Any suggestions would be appreciated.
Hi Mithra, the answer is no, but the viscoelastic properties are still very relevant here. Commonly a sample may start with G' (elastic component) being higher than G" (viscous component) which may be due to weak electrostatic interactions or due to crowding effects (if the solids volume fraction is high) initially. When the gelation process starts at a certain temperature, both moduli will grow and the phase angle will usually drop slightly. If the phase angle doesn't drop significantly during the gelation at all, one may question whether this is technically a gelation process, or just an increase in chain length (MW) or change of conformation.
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