Synthesis and characterization of poly(2-hydroxyethyl methacrylate)/silver hydrogel nanocomposites prepared via in situ radical polymerization

Nanocomposites of poly(2-hydroxyethyl methacrylate), PHEMA, hydrogels with silver nanoparticles (Ag NPs) were produced using an in-situ bulk radical polymerization technique. The reduction of Ag+ precursors to Ag NPs took place during the reaction exclusively by the hydroxyl and carbonyl groups present in HEMA monomer. The formation of silver nanoparticles was identified using XRD characteristic peaks and the surface Plasmon resonance vibration, from UV-vis spectra. FTIR data showed that the inclusion of Ag NPs in the polymer matrix affects the chemical bonds present in the polymer matrix. The thermal stability of the nanocomposites was slightly decreased compared to neat PHEMA, whereas their thermomechanical properties (i.e. elastic modulus) and the glass transition temperature were increased with the amount of the Ag NPs. The polymerization activation energy of the nanocomposites, as calculated from differential isoconversional methods using non-isothermal DSC experiments, was found to vary with conversion in a different way compared to neat PHEMA. These observations were explained based on the destruction of the hydrogen bonds between the hydroxyl and either hydroxyl or carbonyl groups originally existing in neat PHEMA from the formation of the silver aggregates and their binding to the macromolecular chain. (C) 2016 Elsevier B.V. All rights reserved.