Encapsulation of organomodified montmorillonite with PMMA via in situ SR&NI ATRP in miniemulsion

Encapsulation of organomodified montmorillonite within poly (methyl methacrylate) via in situ atom transfer radical polymerization with simultaneous reverse and normal initiation system (SR&NI ATRP) was successfully performed. Miniemulsion polymerization technique has been employed for its abundant advantages to encapsulate inorganic materials. Successful SR&NI ATRP was carried out using 4,4'-dinonyl-2,2'-bipyridine (dNbPy) as a hydrophobic ligand and cetyltrimethylammonium bromide (CTAB) as an effective cationic surfactant at high temperatures. Homogeneous distribution of droplets and particles with sizes in the range of around 170 nm was evaluated by dynamic light scattering (DLS) analysis. Final monomer conversion and molecular weight were determined by gravimetry and size exclusion chromatography (SEC) respectively. By increasing nanoclay content, conversion and molecular weight of nanocomposites decreased. Meanwhile, an increase in PDI values was also observed. X-ray diffraction (XRD) analysis results display organoclay layers disordered and delaminated in the polymer matrix. Thermal stability improvement of all the nanocomposites in comparison with the neat polymer was revealed by thermogravimetric analysis (TGA). Homogeneous distribution of spherical particles with sizes in the range of 170 nm was demonstrated by scanning electron microscopy (SEM) images. These results are complied with the DLS results. Transmission electron microscopy (TEM) image display a dispersion of partially exfoliated clay stacks in the matrix of PMNM 2.