K. Lahrech1*, A. Safouane1, S. Haouache2
1E.S.T, Université de Fès, Maroc
2F.S.T, Université de Fès, Maroc
* Corresponding author. E-mail : email@example.com
Received : 16 July 2002; revised version accepted : 10 December 2002
A gelation process in polyacrylamide solutions is studied by static light scattering measurements at different concentrations and different scattering angles. By examining the temporal variation of the light scattered intensity I(t) from the samples undergoing the transition, we find that at the first stage of gelation, the scattered intensity is a linear function of time and the formed aggregates are linear chains. After this initial period, a crossover occurs; the aggregates become branched and their mass grows as a power law in time. At this stage, the total scattered intensity is well described by the dynamic droplets aggregation model. The analysis of the data shows that the gelation process is governed by an irreversible aggregation limited by reaction and characterized by a fractal dimension Df= 2.1 and a polydispersion coefficient t = 1.5.
Keywords: Gelation process; Aggregation kinetics; Polyacrylamide; Fractal; Light scattering.