Effect of PEO on the network structure of PVA hydrogels prepared by freezing/thawing method

Abstract

Poly(vinyl alcohol) (PVA)/poly(ethylene oxide) (PEO) hydrogels were prepared by freezing/thawing method for application as a wound dressing. The effect of PEO content on the network structure of PVA hydrogel was investigated in terms of crystalline and reological properties. It was found that a low amount of PVA crystallites were present in PVA/PEO hydrogels. With increasing content of PEO, the crstallinity of PVA hydrogel decreased, but the apparent dimensions of crystallites increased. The shear storage modulus (G 0 ) decreased slightly with the increasing temperature within 30-50 C, probably resulting from the breaking of the hydrogen bonding; while it decreased sharply within 50-70 C, probably resulting from the melt of the crystallites of PVA hydrogel. The physical crosslinking density (D pc ) increased with decreasing PEO content, while decreased more dramatically with increasing temperature, indicating that hydrogen bonding was easier to be broken at high temperature. At very low strain amplitudes, the loss modulus (G 00 ) of the hydrogel is lower than the storage modulus (G 0 ) and G 0 is independent of the strain amplitude, indicating that the deformation imposed on the network structure is entirely reversible. With increasing content of PEO, G 0 at low frequency decreased, and the mesh size (L c ) increased, indicating of the decrease of the physical crosslinking density of PVA/PEO hydrogels.

Poly(vinylalcohol)-borate hydrogels with improved features for the cleaning of cultural heritage surfaces

“…We can therefore exclude that PEO can compete with the vinyl alcohol units for reacting with borate ions. From literature studies it is known that PEO acts as a porogen agent in PVA/borax membranes [23] and in PVA gels obtained with freezing/thawing method [24]. In the latter work is reported that addition of PEO in a PVA/water system causes the decrease of PVA degree of crystallinity resulting in the increase of network mesh size and decrease of the storage modulus.…”

“…In the present study we have investigated the effect of adding poly(ethyleneoxide) (PEO) in various concentrations on the mechanical properties of PVA/borax gels and its influence on the capability of retaining organic solvents. PEO is a water-soluble and biocompatible thermoplastic polymer and the literature suggests that it causes an increment of the pores size in PVA/borax hydrogels [23,24] with increasing, at the same time, the mechanical properties. For the above reasons PEO could be a suitable additive for improving the physical characteristics of PVA/borax hydrogels, and possible positive interactions with the miscible organic solvents used in conservation applications.…”

A Biomimetic Poly(vinyl alcohol)–Carrageenan Composite Scaffold with Oriented Microarchitecture

“…So the degree of crystallinity has an effect on the crosslink density in polymer network. 41 As a consequence, relatively high crystallinity of oriented scaffold reveals a more compact network structure in polymeric matrix to accommodate water. Generally, the scaffold should possess the ability to sustain the structural integrity under certain compression, which is necessary to protect the cells or neo-tissue within scaffold from damage.…”

Synthesis of cationic chitosan hydrogel and its controlled glucose-responsive drug release behavior

“…The test methods employed were oscillatory frequency sweep [14]. The hydrogels were subjected to a frequency sweep in the range from 0.01 to 100 Hz at a fixed shear stress (10 Pa) and temperature (25°C).…”