Resumen:
Hydrogels are polymeric materials that exhibit the ability to absorb huge volumes of water. In addition, the water
absorption is reversible and dependent of the swelling conditions (pH, T, etc). As consequence of these properties,
these kind of polymeric network have received attention as materials for biological, biomedical, pharmaceutical and
agricultural applications. The knowledge of the swelling, the diffusion processes, the networks parameters that define
its structure and the rheological properties in different conditions are very important since they will define their
possible applications. In this work we present the synthesis and characterization of new hydrogels based in a new
dendritic monomer with three acid groups (synthesized in our laboratory) with different amount of a crosslinking agent.
Besides, thinking in useful application the studies of their properties were examined. The amount of fluid absorbed was
evaluated for each hydrogel in water and at different pH. The swelling behavior was dependent of the amount of
crosslinking agent and the pH of the fluid absorbed. More amount of crosslinking agent into hydrogel structures
presented less equilibrium swelling ratio capacity (%SRe)in all swelling media. The major %SRe was obtained in
deionizated water. Besides, the hydrogels had different %SRe at distinct pHs (from buffer solutions). The major
swelling capacity was found at pH 7 and the minor at pH 3. At pH 7, the hydrogel is negatively charged and produces
repulsion of charges that generates expansion of the network and more absorption of fluid. On the other hand, at pH 3
the hydrogel is totally protonated and the repulsion charge effect disappears, so the hydrogels are less swelled. The
elastic moduli G' of the swelled matrices (at 25ºC in deionized) water were measured in a rotational rheometer. The
strain sweeps and frequency sweeps tests were performed on each sample to determine the linear viscoelastic region
profiles and viscoelastic performance in a range of frequencies. As expect, the material with more amount of
crosslinking agent presented a critical shear stress (limit of linear response) some times larger than the other hydrogels.
The frequency sweep test showed that the storage modulus are practically not influenced by the frequency of oscillation
for the hydrogels in the range of frequency assayed (0.1-100 s-1). The hydrogels developed in this study exhibit pHdependent
swelling and good viscoelastic properties suggesting that they have potential applications in various fields.