화학공학소재연구정보센터
Macromolecular Rapid Communications, Vol.26, No.20, 1626-1632, 2005
Gelation studies, 4 - Why do "classical" methods like oscillatory shear rheology and dynamic light scattering for characterization of the gelation threshold sometimes not provide identical results especially on thermoreversible gels?
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 g(2)(t) - 1 proportional to t(-mu) and in the oscillatory shear experiment G'(omega) proportional to G ''(omega) proportional to omega(n). 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.