Summary: The sol–gel transition of two thermoreversible gelling mixtures made of xanthan gum and locust‐bean gum has been studied by using in situ, time‐resolved dynamic light scattering (DLS) and in situ rheology. A critical dynamical behavior was observed near the sol–gel transition, which was characterized by the presence of power‐law spectra over three and four decades in the time‐intensity correlation function g2(t) − 1 ∼ t−μ and over four and three decades in the oscillatory shear experiment G′(ω) ∼ G″(ω) ∼ ωn. A comparison of the critical exponents obtained (μ1 ≈ 0.36, μ2 ≈ 0.32 and n1 ≈ 0.62, n2 ≈ 0.67) was made as a function of the dependence of the two mixing ratios according to the theory by Doi and Onuki. New experiments were also performed to compare the critical exponents on such a thermoreversible system.

Summary: In a recent paper [S. Richter et al., Macromol. Rapid Commun. 2004, 25, 1504] the sol‐gel transition of two thermoreversible gelling mixtures made of xanthan gum and locust bean gum has been studied by using time‐resolved dynamic light scattering (DLS) and low‐amplitude oscillatory shear rheology, and is indicated by the presence of the typical power‐law behaviors in the time‐intensity correlation function g2(t) − 1 ∝ t−µ and in the oscillatory shear experiment G′(ω) ∝ G″(ω) ∝ ωn. A significant and reproducible difference of 7 K for the estimated gelation temperatures was found again, with the higher one always determined by rheology. We now present a logical explanation together with new results obtained on this system that may also be of importance for other ones. The incipient infinite percolated cluster that is formed during the gelation process is more pronounced, and is detectable earlier by rheology than by DLS for this present system.Double‐logarithmic plot of the time‐intensity correlation functions g2(t) − 1 versus the delay time t and at a scattering angle of θ = 90° and at several temperatures of the mixture.imageDouble‐logarithmic plot of the time‐intensity correlation functions g2(t) − 1 versus the delay time t and at a scattering angle of θ = 90° and at several temperatures of the mixture.