Sol-Gel Transition & Gelling Behavior

The sol-gel transition is a critical phenomenon in material science and rheology, referring to the transformation of a material from a liquid-like sol (a colloidal suspension or polymer solution) into a solid-like gel. This transition occurs when molecules within the sol form a three-dimensional network that spans the entire system, restricting flow and imparting elastic properties to the material. It is a key process in the formulation and performance of products such as food gels, biomedical hydrogels, cosmetics, adhesives, and pharmaceutical delivery systems.

From a rheological standpoint, the sol-gel transition reflects a shift from viscous-dominated behavior (liquid-like) to elastic-dominated behavior (solid-like). This is characterized by changes in viscoelastic parameters, specifically the storage modulus (G’) and loss modulus (G”), which represent the material’s elastic and viscous responses, respectively. During the transition, G’ and G” often intersect at a critical point known as the gel point, indicating the onset of gelation where the material behaves neither as a pure liquid nor a pure solid but exhibits a balanced viscoelastic structure.

Turnaround time: 1 – 10 days

Rheological Measurement of Gelation

Rheology provides powerful tools to monitor and quantify the sol-gel transition. The most common method involves oscillatory rheometry, where a small sinusoidal deformation is applied to the material, and the response is analyzed. By performing temperature sweeps, time sweeps, or frequency sweeps, one can track the evolution of G’ and G” and identify the gel point.

Time sweeps are conducted at constant frequency and temperature to monitor gelation kinetics. G’ and G” are recorded over time, and the gel point is typically identified when G’ equals G”, or when G’ shows a sudden increase and becomes greater than G”.
Temperature sweeps are useful for thermally induced gelation. The sample is subjected to a controlled temperature ramp, and G’, G”, and tan δ (G”/G’) are recorded. A decrease in tan δ and a crossover of G’ and G” often mark the gelation temperature.
Frequency sweeps can be performed before and after gelation to characterize the structure of the material. At the gel point, G’ and G” both become nearly independent of frequency, which is a hallmark of critical gel behavior.

In some cases, rheological measurements are combined with creep-recovery tests or stress relaxation to further evaluate the mechanical stability and network formation in gels. These data provide insight into gel strength, elasticity, and reversibility—essential parameters for designing and controlling products in food, biomedical, cosmetic, and industrial applications.

Let's get in touch

Still have questions? Our team is here to help. Let us know how we can help and we will get back to you shortly!
By filling out this information, you are adhering to our privacy policy.

Submit your sample for testing

For returning customers, download the Sample Submission Form and send it back to us.