Poly(acrylonitrile) microspheres with a narrow size distribution: Synthesis by single-step swelling and properties

Poly(acrylonitrile)-poly(styrene) micrometer-sized composite particles with a narrow size distribution are prepared by single-step swelling of poly(styrene) uniform template microspheres in emulsion droplets of methylene chloride containing an acrylonitrile monomer and a benzoyl peroxide initiator. Methylene chloride is carefully evaporated with subsequent polymerization of acrylonitrile at a temperature of 70 degrees C inside the shrunken template particles. Acrylonitrile is also polymerized at the particle surface due to the interaction of surface poly(acrylonitrile) oligoradicals with acrylonitrile dissolved in the aqueous phase. Uniform poly(acrylonitrile) particles with a larger surface area are formed by dissolving template poly(styrene) of the composite particles. The surface and bulk properties of the particles are investigated using Fourier transform IR (FTIR) spectroscopy, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction, X-ray photoelectron spectroscopy (XPS), contact-angle measurements, optical microscopy, scanning electron microscopy (SEM), and cross-sectional transmission electron microscopy (TEM).