Preparation, structure, and properties of poly(vinyl acetate‐co‐methyl methacrylate) nanocomposite microspheres with exfoliated montmorillonite through using two‐stage in situ suspension polymerization

Effective encapsulation of montmorillonite intermediate particles (I‐MMT) within poly (vinyl acetate‐co‐methyl methacrylate) (PVAMMA) copolymer by in situ suspension polymerization was performed. The I‐MMT encapsulation, layer exfoliation behavior, chemical composition, particle size distribution and thermostability of PVAMMA/I‐MMT nanocomposite microspheres were characterized by electron microscopies, X‐ray diffraction (XRD), laser particle analyzer, and thermogravimetric analysis (TGA). Swelling behaviors of the nanocomposite microspheres in various cationic salt solutions (NaCl and CaCl₂) and anionic salt solution (NaCl and Na₂SO₄) were also investigated. Results showed that the properties of layer dispersion surface and expansion of these nanocomposite microspheres were well achieved. The synthetic yields of the nanocomposites decreased as the I‐MMT loading increased. These nanocomposite microspheres had an average size from 96.8 μm to 138.4 μm with narrow particle size distribution, loose, and porous surface morphology. XRD patterns clearly proved the exfoliation of MMT layers in the copolymer matrix, which was consistent with TEM analysis. These nanocomposite microspheres showed higher negative zeta potential and higher thermal stability than those of the copolymer microspheres, which was due to the layer exfoliations in encapsulated microspheres. These selected microspheres with 10 to 70 μm diameters provided effectively plugging in the micrometer‐sized core channels through deformation and migration process in plugging experiments, which made them be the candidate materials for modifying the porous reservoir to enhance oil recovery in petroleum engineering. POLYM. COMPOS., 35:1104–1116, 2014. © 2013 Society of Plastics Engineers