Tracing Chemical Crosslinking Reaction of Dextran by Oscillatory Rheometry: Effect of Temperature and Crosslinker Concentration on the Gel Point

Crosslinked dextran (Dex) hydrogels can be fabricated by crosslinking of the polymer dissolved in an aqueous semidilute alkaline solution using epichlorohydrin (ECH) as acrosslinker. These hydrogels are highly versatile, biocompatible, non-toxic and bioerodible. Physicochemical properties of the hydrogels strongly correlate to their microstructure and could provide useful information for modulating their performance affecting bioactive agent(s)delivery profile. Viscoelastic properties of polymeric systems undergoing gelation can be monitored rheometrically with virtually no disturbance in their microstructure.Here, oscillatory shear experiments are performed for continuous tracing of the viscoelastic properties associated with Dex cross-linking reaction and characterizing the mechanical properties of the resulting networks. To this end, the dependence of Dex crosslinking reaction is reported as afunction of the reaction temperature and the cross-linker concentration. Some important parameters like the apparentactivation energy (Ea), time necessary to pass the sol-gel phase transition, networks fractal dimension, and critical exponents of power-law model were determined in different experimental conditions of the cross-linking reaction