Molecular-scale investigation of polymerization, nucleation and growth of polystyrene particle by atomic force microscopy

To clarify the mechanism of the nucleation and growth processes in the soap-free polymerization of polystyrene latex particles in water, the polymerization process was investigated on a molecular scale, by using an atomic force microscope (AFM), as well as a scanning electron microscope (SEM) and a dynamic light scattering apparatus (DLS). A 'cationic' initiator was employed to make all the polymeric materials produced, such as oligomers, embryos, nuclei, and grown particles, adsorb electrostatically on the negatively charged mica plate of molecular-scale smoothness. This in situ transfer of polymeric materials in the bulk onto the mica surface enables us to observe the images of polymeric materials during the reaction process and to estimate what is happening in the nucleation and growth processes of particles, at least qualitatively. The most important findings of the present study are that, these molecular-scale polymeric materials, to which much attention has not been paid probably because of the difficulty of detection, are continuously born in the bulk throughout the reaction process of particle formation, and 21 they play an important role in the growth of particles. (C) 2008 Curtin University of Technology and John Wiley & Sons, Ltd.