Synthesis, characterization and reaction kinetics of PMMA/silver nanocomposites prepared via in situ radical polymerization

In this investigation, nanocomposites of poly(methyl methacrylate), PMMA, with silver nano-particles (Ag NPs) were produced using an in-situ radical polymerization technique, where the reduction of Ag⁺ precursors takes place during the reaction. The effect of silver NPs on the reaction kinetics is investigated by measuring the variation of conversion with time and the molecular weight distribution of the polymer formed. The properties of the PMMA/Ag nano-hybrids were measured using a variety of techniques including, X-ray diffraction, FTIR and UV-Vis spectrometry, thermogravimetric analysis and differential scanning calorimetry. FTIR data showed that the inclusion of Ag NPs in the polymer matrix was rather physical without a strong chemical bond. Silver nanoparticles with average diameter ranging from 37 to 47 nm were identified with broader size distribution observed at higher amounts of silver added. The in situ formation of Ag NPs from the reduction of Ag⁺ was explained based on a radical reaction mechanism and chain transfer reactions. It was found that the initiator efficiency is reduced by the presence of the Ag NPs, resulting in a reduction of the reaction rate and a slight increase in the number average molecular weight of the polymer formed. The polydispersity of the MWD as well as the glass transition temperature of the polymer was found to decrease with the amount of the NPs. Finally, from thermogravimetric analysis, it was verified that the presence of the NPs results in macromolecular chains with less defect structures.