Triple Stimuli Responsive Poly(vinyl alcohol)Chitosan/Nanoclay/Nanosilver Nanocomposite Hydrogel

Sensitizing the nanocomposite hydrogel systems to multiple stimuli ensures increasing their efficiency from the viewpoint of the magnitude and rate of response of the system. Adding nanosilver to dual stimuli (pH and temperature) responsive chitosan/poly(vinyl alcohol)/nanoclay nanocomposite hydrogel system increases the sensitivity of the chosen system to the third stimulus, i.e. the electric field, and enhances the overall rate of response of the system. The reduction of a silver salt to silver nanoparticles was performed by a green synthesis method within the nanocomposite hydrogel system using chitosan as a reducing agent and polyvinyl alcohol as a stabilizer. Silver nanoparticle formation was investigated by UV-vis spectroscopy. SEM was used to study the distribution of silver nanoparticles in the nanocomposite system. The structural characterization of nanocomposite hydrogel was carried out by FTIR. Cyclic voltammetry was employed to evaluate the conductivity of the system. The peak observed at the wavelength of 410 nm confirmed the synthesis of nanosilver. The SEM micrograph showed the uniform distribution of nanosilver in the system. The results of the sensitivity of the responsive system to multiple stimuli indicated that the nanosilver increased the rate of response of the system in acidic and alkaline solutions. The maximum swelling rate of the system was at pH 2 and the temperature of 55°C, while the minimum rate was at pH 5 and the temperature of 20°C. The presence of nanosilver increased the rate of response of dual stimuli (pH and temperature) responsive system up to three times and its swelling rate to 1.5 times. By applying an electric field at pH 2, the time of response of system decreased from hours to minutes and its swelling ratio increased up to 1.7 times.