Characterization of gelification of chitosan solutions by dynamic light scattering

Gels consist of soft materials with vast use in several activities, such as pharmaceutical industry, food manufacturing, and coatings/textile applications. In order to obtain these materials, the process of gelification, which can be physical (based on physical interactions) and/or chemical (based on covalent crosslinking), has to be carried out. In this manuscript we used dynamic light scattering (DLS) and rheometry to monitor the covalent gelification of chitosan solutions by glutaraldehyde. Intensity correlation function (ICF) data was obtained from DLS and the exponential stretched Kohrausch-William-Watts (KWW) function was fitted to them. A correlation between the parameters of KWW equation and delay time was explained in terms of viscoelastic changes during the process of gelation, caused by, at a first stage, the increase of chitosan macromolecular dimensions and, at longer times, by the increase in chitosan crosslinking density and loss of ergodicity. The dependence between apparent viscosity on reaction time was used to support the discussion proposed in this work. (C) 2011 Elsevier Ltd. All rights reserved.