Viscoelasticity of radiation-formed PVA/PVP hydrogel

Abstract

The dynamic rheological behaviour of gamma-irradiated 12.8 wt% poly(vinyl alcohol) (PVA), 12.8 wt% poly(vinyl pyrrolidone) (PVP), and a blend of 8 wt% PVA and 4.8 wt% PVP aqueous solutions have been studied pre- and post-gelation. The non-irradiated solutions displayed rheological behaviour typical of dilute to semi-dilute polymer solutions, with the complex viscosity being independent of the frequency and shear rate (i.e. Newtonian behaviour) over the range of frequencies tested and the loss modulus G"(omega) and storage modulus G'(omega) being nearly proportional to omega and omega2, respectively. After a set of doses of gamma-radiation, the magnitudes of the dynamic moduli G'(omega) and G"(omega) increased as the absorbed dose increased, with notable differences between the two homopolymers and the blend. The stages of gelation were effectively monitored by means of dynamic rheological measurements, allowing the possible mechanisms of network formation to be elucidated. The doses required for gelation of the PVA, PVP, and blend samples, determined on the basis of the Winter and Chambon criteria for gelation, were found to be 12 kGy for the 12.8 wt% PVA, 4 kGy for the 12.8 wt% PVP, and 5 kGy for the 8 wt% PVA/4.8 wt% PVP solutions. The unexpected lower gelation dose demonstrated by the blend sample, compared with predictions based on the blend composition, and the associated gelation mechanism are also discussed.

Self-reinforcement and protein sustained delivery of hyaluronan hydrogel by tailoring a dually cross-linked network

“…5 showed the rheological properties of various HA-based hydrogels at low-frequencies. For all the hydrogels, the storage modulus (G′) was independent of the frequency, confirming the covalent nature of these hydrogels; meanwhile G′ values were over ten times higher than G″ values, indicating that these hydrogels mainly exhibited elasticity [33,34]. Among them, BGs showed the lowest G′ of 1600 Pa, but it was raised to~3700 Pa after blending with HGPs-1.5.…”

Photo-crosslinking hyaluronan-heparin hybrid hydrogels for BMP-2 sustained delivery

“…Figure 5 shows the rheological properties of various hydrogels at low frequencies. All of the hydrogels presented a storage modulus (G′) independent of frequency, indicative of the covalent nature; meanwhile G′ values were much higher than the loss modulus (G″) values, suggesting that elasticity dominated these hydrogels [26,27]. This typical elasticity of soft hydrogels mimicking the elastic extracellular matrix is advantageous to cell attachment and proliferation [24].…”

Improving the homogeneity of tissue‐mimicking cryogel phantoms for medical imaging

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