Thermo-responsive behavior of radiation-induced poly(N-isopropylacrylamide)/polyethylene oxide nanocomposite

Abstract

Temperature-sensitive poly(N-isopropylacrylamide)/polyethylene oxide (PNIPAAm/PEO) nanocomposite hydrogels were successfully synthesized using γ-radiation as the initiator and crosslinking agent. The temperature-dependent swelling and shrinking behavior of PNIPAAm/PEO was exploited in order to form silver nanoparticles within the hydrogel network. Loading-temperature-responsive hybrid microgels containing silver nanoparticles (AgNPs) were readily prepared by the in situ reduction of Ag+ ions within and coordinated to PNIPAAm/PEO hydrogels. A novel method—irradiation—was utilized to generate AgNPs within the previously obtained hydrogel matrix. The newly prepared Ag-NPs/PNIPAAm/PEO hydrogels exhibited much better temperature-sensitive properties than conventional polymers. The PNIPAAm hydrogels thus prepared exhibited properties such as pore size, equilibrium swelling ratio, and swelling/deswelling rates that could be varied by modifying the feed weight ratio of NIPAAm to PEO. UV-Vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) measurements confirmed that the hydrogel possessed nanostructure, and FTIR was employed to characterize the components of the resulting nanoobjects. The hydrodynamic diameter and morphology of the microgel particles were examined by dynamic light scattering (DLS) and scanning electron microscopy (SEM), respectively. At room temperature, the hydrodynamic diameter of the PNIPAAm/PEO polymer was measured as 3.0 ± 0.7 μm, while that of the PNIPAAm/PEO-stabilized AgNPs was found to be 1.8 ± 0.1 μm. Twenty-five percent of the silver nanoparticles were less than 64.9 nm in diameter, and the mean of the particle size was 9.6 nm. These stimuli-responsive nanocomposite hydrogels have potential applications in biomedicine; for example, they could be used as drug-delivery matrices.