Rheological behaviors and secondary networks of polyacrylamide hydrogel filled with silica

Abstract

Polyacrylamide (PAM) hydrogel filled with different types and contents of hydrophilic silica was synthesized by in situ polymerization. Rheological behaviors of the hydrogels were measured with an oscillation rheometer. The results indicated that the addition of silica efficiently improved the mechanical properties of the hydrogel, both for the uncrosslinked system and crosslinked system; simultaneously, the storage modulus (G 0 ), loss tangent (tand) and viscosity (g) of the hydrogel were obtained. These results suggest that a nonbonded complexation existed between the silica and the molecular chains of PAM that endowed the hydrogel with special behaviors. Results from Fourier Transform infrared spectroscopy (FTIR) showed that the action of the nonbonded complexation was derived from hydrogen bonds between hydroxyl groups of silica and amide groups of PAM. The formed secondary networks endowed the hydrogels with high mechanical properties.

Injectable Thermosensitive Nanocomposites Based on Poly(N-vinylcaprolactam) and Silica Particles for Localized Release of Hydrophilic and Hydrophobic Drugs

“…This improvement can be explained by the creation of an interconnected network of polymeric chains and silica, which contributed to the increase in the elastic portion of the nanocomposite. 33 By analyzing Figure 4f, it is possible to see that there is no difference in the values of complex viscosity after the addition of the nanoparticles at room temperature. The low values of viscosity indicate that these solutions at a concentration of 20 wt % can be used as injectable systems, since the materials used for injectable applications need to present a low viscosity to allow their administration by syringe.…”

“…The addition of the nanospheres in the percentage of 5% increased G ′ and G ″ in 35 and 50%, respectively, in comparison to the pure polymer. This improvement can be explained by the creation of an interconnected network of polymeric chains and silica, which contributed to the increase in the elastic portion of the nanocomposite …”

“…This improvement can be explained by the creation of an interconnected network of polymeric chains and silica, which contributed to the increase in the elastic portion of the nanocomposite. 33 …”