Properties of thermoreversible gels

In a short survey chemical and physical aspects characterising thermoreversibly gelling systems are gathered. Rheological properties of the system gelatin/water for different polymer concentrations at various temperatures and varying angular frequencies are presented. The results are interpreted following the percolation theory. The relevant exponents of the storage and loss modulus are close to the percolation model of Arbabi and Sahimi. The pre‐gel properties favour the Zimm‐limit whereas the post‐gel properties are close to the Rouse‐limit. This controversial behaviour is discussed. The gel‐point has been determined by the divergence criterion of the dynamic viscosity at zero frequency when the storage modulus vanishes. The critical times in the percolation results agree fairly well with the time of gelation but not with the cross over time of the storage and loss modulus curves versus time at zero frequency. An equilibrium aggregation model for the post gelation processes is presented which is based on the percolation approach. The time dependence of the storage modulus can be described in the total time range between gel point and the final equilibrium value after very long times.