Gelation Studies: Comparison of the Critical Exponents Obtained by Dynamic Light Scattering and Rheology, 2

Abstract

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.

Recent Gelation Studies on Irreversible and Reversible Systems with Dynamic Light Scattering and Rheology ‐ A Concise Summary

“…Similar extended DLS and rheology studies to prove the validity of Equation (8) were performed on other thermoreversible systems (three mixtures made of xanthan gum and locust bean gum [29,42] (XG/LBG), and gelatin [30] ). The advantage of studying thermoreversible gelation over radical cross-linking reactions is that the gelation process is only influenced by temperature, which can be held constant to have enough measuring time for rheological and DLS investigations.…”

“…0.19 as reported by different authors. [26][27][28][29][30] Here IðtÞ h i is the scattering intensity at time t, and a given scattering vector q with respect to t ¼ 0 as well as . .…”

“…As an overall result, the prediction of Equation (8) is not valid! It must be mentioned that the difference in the estimated gelation temperature (power-law behavior in the oscillatory shear experiment and in the TCFs in the DLS) on all mixtures made of xanthan gum and locust bean gum was 5-7 K. [29,42] The higher sol-gel transition temperature indicated by the power-law scaling was always estimated by rheology. The reasons for this unusual behavior, which was observed for the first time, are given briefly in the conclusion section; for more details see ref.…”

A New Vesicle-loaded Hydrogel System Suitable for Topical Applications: Preparation and Characterization

“…when xanth is dissolved as single chains. However, a wide debate is still open in elucidating the mechanism leading to the gel formation and several models were proposed (17)(18)(19)(20)(21).…”

Gel Point Determination of TEOS-Based Polymeric Materials with Application on Conservation of Cultural Heritage Buildings

“…The previously mentioned techniques can be used to characterize the sol-gel process under interest, but they not always agree with each other [26]. To discard possible differences among different techniques, we characterize the gel point of our novel material by rheological measurements and light scattering techniques.…”