engleski

Thermal, magnetic and rheological properties of poly(ethylene oxide)/iron oxide nanocomposite hydrogels synthesized using one-step gamma-irradiation technique

Magnetic polymer gels (ferrogels) are new promising class of nanocomposite hydrogels, with potential application in soft actuators such as artificial muscles, in tissue engineering, drug delivery, hyperthermia applications etc. Although gamma-irradiation method is highly suitable for generation of nanoparticles (NPs) in a solution as well as for the formation of three-dimensional polymer network, i.e. hydrogels, the radiolytical syntheses of iron oxide/polymer nanocomposite gels are rarely investigated. One of the reasons is very complex iron oxide chemistry that produced numerous iron oxide and oxyhydroxide polymorphs. Usually, nanocomposite gels are synthesized by two-step methods (crosslinking with pre-prepared NPs or in situ NPs synthesis within polymer gel), however, in this work we used radiolytical one-step synthesis. One-pot synthesis takes an advantage of simultaneous crosslinking and reduction of metal salts, which is quicker and simpler, and results in small NPs size and narrow size distribution. The aim of this study is to explore the ability of radiation technique to synthesize PEO/Fe-oxide nanocomposite hydrogels in a single-step as well as to investigate the thermal, magnetic and rheological properties of such synthesized gels. The PEO/iron oxide nanocomposite hydrogels were synthesized by γ-irradiation of PEO and iron(III) chloride alkaline aqueous solutions. The dose, pH, concentration of Fe3+ and 2-propanol were varied and optimised. Gels synthesized without 2-propanol were firm brittle and compact, but with almost no changes in iron(III) precursor phase (no reduction). In contrast, irradiation in the presence of 2-propanol resulted in more flexible brittle (more gummy) gels with more reduced iron oxide phases. At higher Fe3+ concentration and 2-propanol black magnetic hydrogels with embedded magnetite/maghemite NPs were obtained, as confirmed by XRD, SEM, Mössbauer spectroscopy. Further increase in 2-propanol resulted in black highly magnetic suspensions. DSC and rheological measurements showed that thermal and viscoelastic properties and structural strength of the gels depended on the dose, as well as amount of nanoparticles synthesized inside gels. Both enthalpies and temperatures of melting and crystallization of gels decrease with the dose and the amount of NPs.

PEO ; iron oxide ; nanocomposites ; gamma-irradiation ; synthesis ; rheology ; DSC

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