Preparation of styrene/acrylic acid copolymer microspheres: polymerization mechanism and carboxyl group distribution

 Poly(styrene-co-acrylic acid) (St/AA) copolymer microspheres were prepared by batch emulsifier-free emulsion copolymerization of St with AA. The monomer conversion, the morphology and the composition of the particles along the polymerization process were monitored by a gravimetric method, transmission electron microscopy observation and Fourier transform IR analysis, respectively. A shift of the polymerization locus from inside the particles to “outside” the particles in the postnucleation stage was proposed. The results of the study of the distribution of carboxyl groups by a combination of elemental and X-ray photoelectron spectroscopy analyses implied a core/shell structure for the St/AA copolymer microspheres. By chemical metal deposition, nickel particles were formed and deposited on the surface of St/AA microspheres, forming polymer/metal composite particles.