Rheological characteristics during chemical gelation of semidilute solutions of dextran in the presence of cross-linking agents of different chain length are reported. Effects of cross-linker chain length on the gel point, structure of the gel network, and mechanical properties were investigated. The rheological results disclose that for all systems, the gelation process proceeds over a long time and both the complex viscosity and the power law exponent reveal that solid-like gel structures are formed in the post-gel region. Water absorption behavior of the gels was studied and the results were interpreted by using a kinetic model indicating that the swelling is diffusion controlled. The findings clearly show that the rheological characteristics, such as the time of gelation and gel strength of dextran hydrogels can be tuned by changing the chain length of the cross-linker agent. Furthermore, the swelling results also exposed significant differences between gels cross-linked with the two different cross-linker agents.
Keywords: Chemical crosslinkers; Dextran hydrogels; Percolated networks; Rheology; Swelling.
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