Abstract
A study has been made of polymerization of styrene, which has little solubility in water, in aqueous solution using potassium persulfate as initiator at the polymerization temperature 70 or 80°C. The results were as follows: 1) At the early stage of polymerization, the particle size distribution is broad, but at the later stage becames narrow due to the mutual precipitation of larger or smaller particles in diameter. 2) As the initiator concentration decreases, the amount of precipitated polymer decreases, the stability of particles increases and the particles with same diameter are formed. 3) In the range of the monomer concentration investigated, the amount conversion at 28.5 hr, increases as the initial monomer concentration increases, then decreases through a maximum value. 4) The particle size and the degree of polymerization decrease as the speed of agitation increases.
From the results obtained above, it was evident that the stable particles with narrow particle size distribution were obtained at the conditions of KPS concentration 6.2×10-4 mol/l, initial monomer concentration 0.871 mol/l, speed of agitation 250 rpm, and polymerization temperature 70°C.
On the other hand by the measurement on electrophoretic mobilities of the particles prepared above, the following results were obtained. The number of charges on a particle surface was equal to the one calculated from the degree of polymerization on the assumption that there were two strong ions at the end of a polymer molecule. From this fact, we led to the conclusions that the termination of polymerization was coupling, ·SO4- as the initiator could not enter into the inner part of the particle and consequently existed only on the surface of particles.
