Ultrasound assisted synthesis and characterization of poly(methyl methacrylate)/CaCO3 nanocomposites

The combined effects of sonochemical and conventional chemical initiation on the emulsion polymerization of methyl methacrylate (MMA) and MMA–CaCO3 systems have been studied. Combining ultrasound (US) and conventional initiation by potassium persulfate (KPS) for the MMA and MMA–CaCO3 systems, helped increase the final conversion. An increase of 15% for the MMA only system (from 72% to 87%) and of 10% for the MMA–CaCO3 system (from 76% to 86%) was observed as compared to initiation by KPS alone. Also, an increase of 18% (from 69% to 87%) and 20% (from 66% to 86%) for the MMA only and MMA–CaCO3 systems, respectively was observed for the combined initiation as compared to initiation by US alone. Although all particles synthesized were in the size range of 60–130 nm, the excellent dispersion ability of ultrasound helped to obtain narrow size distribution and smaller average sizes in both the PMMA and PMMA–CaCO3 systems. Possible mechanisms have been proposed for both the polymerization and the formation of poly-MMA–CaCO3 composite and core–shell nanoparticles taking into account the results obtained by analyzing the synthesized materials.

► Combined use of ultrasound and conventional chemical initiation improves final conversion.
► Combined technique offers smaller particle size and narrow size distribution.
► Composite and core–shell particles obtained explained by dual pathway mechanism.