Abstract
Hydrogel nanocomposites containing silver nanoparticles of size 15–21 nm were prepared by diffusion and in-situ chemical reduction in chemically crosslinked polymers based on N-acryloyl-N′-ethyl piperazine (AcrNEP) and N-isopropylacrylamide (NIPAM). The polymer chains of the hydrogel network offered control and stabilization of silver nanoparticles without the need for additional stabilizers. The presence of silver nanoparticles and their size was quantified by UV-Vis absorption spectroscopy and scanning electron microscopy. The nanocomposite hydrogels were responsive to pH and temperature changes of the external environment. The equilibrium weight swelling ratio of the hydrogel nanocomposite was lower in comparison with the precursor hydrogel. Silver nanoparticles present in the nanocomposite offered additional physical crosslinking which influenced media diffusion and penetration velocity. The release of silver nanoparticles from the hydrogel matrix in response to external pH changes was studied. The rate of release of silver nanoparticles was higher in a solution of pH 2.5 due to maximum swelling caused by ionization of the gel network. No significant release of nanoparticles was observed in a solution of pH 7.
Highlights
Hydrogels are three-dimensional crosslinked polymer networks that can absorb large amounts of water and yet remain insoluble
We report the synthesis and characterization of pH- and temperature-responsive silver nanocomposite hydrogels by a facile in-situ method
This study provides the possibility to control the size and quantity of silver nanoparticles in the hydrogel matrix by varying the amount of cationic monomer (AcrNEP) and crosslinker
Summary
Hydrogels are three-dimensional crosslinked (chemical or physical) polymer networks that can absorb large amounts of water and yet remain insoluble. In recent years the synthesis of nanoparticles within a crosslinked polymer network (hydrogels) by in-situ and ex-situ chemical reduction has gained considerable research focus in the development of polymer-metal hybrid materials [14,15,16,17] Such hybrid materials (hydrogel nanocomposites) containing colloidal nanoparticles have wide applications in catalysis, drug-delivery systems, anti-bacterial systems, chemical sensors etc. The nanocomposite hydrogel was synthesized by incorporating silver nanoparticles in the gel matrix by diffusion and in-situ chemical reduction process This in-situ method of synthesis facilitates the formation of nanoparticles in hydrogels with a low size polydispersity index. This study provides the possibility to control the size and quantity of silver nanoparticles in the hydrogel matrix by varying the amount of cationic monomer (AcrNEP) and crosslinker This type of nanocomposite material is non-toxic and envisaged to possess excellent optical and anti-microbial. The influence of external stimuli such as changes in pH on the release of silver nanoparticles from the nanocomposite hydrogel matrix is described in this report
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